Display apparatus incorporating dual-level shutters

ABSTRACT

This disclosure provides systems, methods and apparatus for modulating light to form an image on a display, as well as methods manufacturing such apparatus. The display apparatus includes dual-level shutter assemblies. Each dual-level shutter assembly includes front and rear light obstructing levels positioned adjacent to respective front and rear light blocking layers. The front and rear light blocking layers define apertures providing optical paths from a backlight to the front of the display. The dual-level shutters selectively obstruct these optical paths to generate an image.

TECHNICAL FIELD

This disclosure relates to electromechanical systems (EMS). Inparticular, this disclosure relates to EMS shutter designs.

DESCRIPTION OF THE RELATED TECHNOLOGY

The demand for improved contrast ratio in displays continues toincrease. Certain shutter-based EMS display devices experience decreasedcontrast ratios resulting from light leaking around the light modulatingshutters they include. For example, certain shutter-based EMS displaysinclude shutters that move laterally between two opposing light blockinglayers. The light blocking layers include apertures, which the shuttersselectively obstruct to modulate light. However, typical shutter designsare more effective at obstructing light passing through one of the lightblocking layers than the other. Insufficient obstruction of theapertures in the other light blocking layer can contribute to a reducedcontrast ratio.

Moreover, there are few if any EMS-based light modulators that canreliably achieve discrete partially transmissive states between a fullydark and a fully light state. Thus, displays incorporating EMS-basedlight modulators tend to generate different gray scale values usingprinciples of time division by driving the light modulators into lightor dark states in a series of subframes. Even if such subframes areweighted, such displays may still need to generate a large number ofsubframes per image frame to obtain the level of grayscale granularitydesired.

SUMMARY

The systems, methods and devices of the disclosure each have severalinnovative aspects, no single one of which is solely responsible for thedesirable attributes disclosed herein.

One innovative aspect of the subject matter described in this disclosurecan be implemented in an apparatus that includes a first light blockinglayer and a shutter. The first light blocking layer includes an apertureformed through it. The shutter is configured to be moved laterally alonga first axis with respect to the light blocking layer by at least oneactuator. The shutter can include a first light obstructing portionwhich has a dimension along the first axis that is smaller than adimension of the aperture along the first axis. The shutter alsoincludes a second light obstructing portion that has a dimension alongthe first axis that is greater than or equal to the dimension of theaperture along the first axis. In some implementations, the at least oneactuator is configured to move the shutter into a first state in whichneither the first or the second light obstructing portion substantiallyobstructs light passing through aperture, a second state in which thefirst light obstructing portion obstructs a fraction of light passingthrough the aperture, and a third state in which the second lightobstructing portion obstructs substantially all of the light passingthrough the aperture.

In some implementations, each of the first and second light obstructingportions of the shutter includes a proximal light obstructing and distallight obstructing level, which are connected by sidewalls. In some suchimplementations, the at least one actuator includes an electrodepositioned adjacent the shutter, and the proximal light obstructinglevel is positioned at about the same height over a substrate as aproximal edge of the electrode. In some implementations, the distallight obstructing level is positioned at about the same height over asubstrate as a distal edge of the electrode.

In some implementations, a portion of one of the proximal and distallight obstructing levels is substantially thicker than another portionof the proximal or distal light obstructing level. In some suchimplementations, the thicker portion of the proximal or distal lightobstructing level is at a position in the shutter such that when theshutter is in a closed position, the thicker portion is in alignmentwith the first aperture defined by the first light blocking layer.

In some other implementations, the shutter is configured such that in aclosed position, a portion of the proximal light obstructing leveloverlaps an edge of the first aperture defined in the first lightblocking layer and a portion of the distal light obstructing leveloverlaps an edge of a second aperture defined in a second light blockinglayer. In some such implementations, the second light blocking layer ispositioned on an opposite side of the shutter from the first lightblocking layer. The proximal light obstructing level can be spaced fromthe first light blocking layer by about the same distance as the distallight obstructing level is spaced from the second light blocking layer.In some other implementations, the proximal light obstructing level canbe spaced from the first light blocking layer by a distance that is lessthan about 3 microns different from the distance with which the distallight obstructing level is spaced from a second light blocking layerpositioned opposite the shutter from the first light blocking layer.

In some implementations, the apparatus includes an electrostaticactuator for moving the shutter into and out of an optical path throughthe aperture. In some implementations, the electrostatic actuatorincludes at least one beam electrode positioned adjacent the shutter,and the proximal light obstructing level is positioned at about the sameheight over a substrate as a proximal edge of the beam electrode. Insome implementations, the distal light obstructing level is positionedat about the same height over a substrate as a distal edge of the beamelectrode.

In some implementations, the apparatus includes a display, a processor,and a memory device. The display can include the shutter. The processorcan be configured to communicate with the display and to process imagedata. The memory device is configured to communicate with the processor.In some implementations, the apparatus also includes a driver circuitconfigured to send at least one signal to the display, and the processoris further configured to send at least a portion of the image data tothe driver circuit. In some implementations, the apparatus includes animage source module configured to send the image data to the processor.The image source module can include at least one of a receiver,transceiver, and a transmitter. In some implementations, the apparatuscan also include an input device configured to receive input data and tocommunicate the input data to the processor.

Another innovative aspect of the subject matter described in thisdisclosure can be implemented in a method for fabricating a displayelement. The method includes depositing and patterning a first layer ofsacrificial material over a substrate, depositing a first layer ofstructural material over the patterned first layer of sacrificialmaterial, and patterning the first layer of structural material todefine a proximal light obstructing level of a shutter and to define afirst shutter aperture. The method further includes depositing andpatterning a second layer of sacrificial material over the patternedfirst layer of structural material, depositing a second layer ofstructural material over the patterned second layer of sacrificialmaterial, and patterning the second layer of structural material todefine a distal light obstructing level of the shutter.

In some implementations, patterning the second layer of sacrificialmaterial includes forming a recess in the second layer of sacrificialmaterial extending down to a portion of the first layer of structuralmaterial that forms the proximal light obstructing level of the shutter.In some implementations, depositing the second layer of structuralmaterial includes depositing a portion of the second layer of structuralmaterial directly over a portion of the first layer of structuralmaterial.

In some implementations, the method further includes defining a secondshutter aperture in the second layer of structural material such thatthe second shutter aperture aligns with the first shutter aperturedefined in the first layer of structural material. In some suchimplementations, the second shutter aperture is defined in a portion ofthe second layer of structural material positioned at the top of amaterial stack that includes the substrate, the first layer ofsacrificial material, and the second layer of sacrificial material. Insome other implementations, the second shutter aperture is defined in aportion of the second layer of structural material positioned at thebottom of a recess patterned into the second layer of sacrificialmaterial.

In some implementations, the method further includes removing the firstand second layers of sacrificial material to release the proximal anddistal light obstructing levels. In some other implementations, definingthe proximal light obstructing level and the shutter aperture includesdefining the shutter aperture closer to a first edge of the proximallight obstructing level than to a second, opposing edge of the proximallight obstructing level. In some other implementations, the proximallight obstructing level and the first shutter aperture are defined suchthat a distance between the first shutter aperture and the first edge isabout half the distance between the first shutter aperture and thesecond, opposing edge.

Details of one or more implementations of the subject matter describedin this specification are set forth in the accompanying drawings and thedescription below. Although the examples provided in this summary areprimarily described in terms of MEMS-based displays, the conceptsprovided herein may apply to other types of displays, such as liquidcrystal displays (LCD), organic light emitting diode (OLED) displays,electrophoretic displays, and field emission displays, as well as toother non-display MEMS devices, such as MEMS microphones, sensors, andoptical switches. Other features, aspects, and advantages will becomeapparent from the description, the drawings, and the claims. Note thatthe relative dimensions of the following figures may not be drawn toscale.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A shows a schematic diagram of an example direct-view MEMS-baseddisplay apparatus.

FIG. 1B shows a block diagram of an example host device.

FIG. 2 shows a perspective view of an example shutter-based lightmodulator.

FIG. 3A shows a schematic diagram of an example control matrix.

FIG. 3B shows a perspective view of an example array of shutter-basedlight modulators connected to the control matrix of FIG. 3A.

FIG. 4A and FIG. 4B show views of an example dual actuator shutterassembly.

FIG. 5 shows a cross sectional view of an example display apparatusincorporating shutter-based light modulators.

FIGS. 6A-6E show cross sectional views of stages of construction of anexample composite shutter assembly.

FIGS. 7A-7D show isometric views of stages of construction of an exampleshutter assembly with narrow sidewall beams.

FIG. 8A shows a cross-section view of an example display apparatus.

FIG. 8B shows a perspective view of a shutter assembly incorporated intothe example display apparatus shown in FIG. 8A.

FIG. 9 shows a flow diagram of an example method for fabricating theshutter assembly shown in FIGS. 8A and 8B.

FIGS. 10A-10H show cross sectional views of the results of each of theprocessing stages included in the method shown in FIG. 9.

FIGS. 11A-11C show cross-sectional views of another example displayapparatus.

FIG. 11D shows an example perspective view of the shutter assemblyincorporated into the display apparatus shown in FIGS. 11A-11C.

FIG. 11E shows a perspective view of another example shutter assemblysimilar to the shutter assembly shown in FIGS. 11A-11D.

FIGS. 12A-12H show cross sectional views of example stages of thefabrication of the shutter assembly shown in FIGS. 11A-11D.

FIG. 13 shows a flow diagram of another representation of a method ofmanufacturing the shutter assembly shown in FIGS. 11A-11D.

FIGS. 14 and 15 show system block diagrams of an example display devicethat includes a set of display elements.

Like reference numbers and designations in the various drawings indicatelike elements.

DETAILED DESCRIPTION

The following description is directed to certain implementations for thepurposes of describing the innovative aspects of this disclosure.However, a person having ordinary skill in the art will readilyrecognize that the teachings herein can be applied in a multitude ofdifferent ways. The described implementations may be implemented in anydevice, apparatus, or system that can be configured to display an image,whether in motion (such as video) or stationary (such as still images),and whether textual, graphical or pictorial. More particularly, it iscontemplated that the described implementations may be included in orassociated with a variety of electronic devices such as, but not limitedto: mobile telephones, multimedia Internet enabled cellular telephones,mobile television receivers, wireless devices, smartphones, Bluetooth®devices, personal data assistants (PDAs), wireless electronic mailreceivers, hand-held or portable computers, netbooks, notebooks,smartbooks, tablets, printers, copiers, scanners, facsimile devices,global positioning system (GPS) receivers/navigators, cameras, digitalmedia players (such as MP3 players), camcorders, game consoles, wristwatches, clocks, calculators, television monitors, flat panel displays,electronic reading devices (such ase-readers), computer monitors, autodisplays (including odometer and speedometer displays, etc.), cockpitcontrols and/or displays, camera view displays (such as the display of arear view camera in a vehicle), electronic photographs, electronicbillboards or signs, projectors, architectural structures, microwaves,refrigerators, stereo systems, cassette recorders or players, DVDplayers, CD players, VCRs, radios, portable memory chips, washers,dryers, washer/dryers, parking meters, packaging (such as inelectromechanical systems (EMS) applications includingmicroelectromechanical systems (MEMS) applications, as well as non-EMSapplications), aesthetic structures (such as display of images on apiece of jewelry or clothing) and a variety of EMS devices. Theteachings herein also can be used in non-display applications such as,but not limited to, electronic switching devices, radio frequencyfilters, sensors, accelerometers, gyroscopes, motion-sensing devices,magnetometers, inertial components for consumer electronics, parts ofconsumer electronics products, varactors, liquid crystal devices,electrophoretic devices, drive schemes, manufacturing processes andelectronic test equipment. Thus, the teachings are not intended to belimited to the implementations depicted solely in the Figures, butinstead have wide applicability as will be readily apparent to onehaving ordinary skill in the art.

Display contrast ratio can be improved in shutter-based EMS displays byincorporating shutters that have both front and rear light obstructinglevels. One of the light obstructing levels is located proximate to asubstrate on which the shutter is fabricated. The other lightobstructing level is positioned distally from the substrate with respectto the other light obstructing level. Each light obstructing level ispositioned relatively close to an adjacent light blocking layer. Giventhe relatively small distances between the light obstructing levels andthe adjacent light blocking layers, the shutter is able to moreeffectively block light passing through apertures defined through bothlight blocking layers.

Particular implementations of the subject matter described in thisdisclosure can be implemented to realize one or more of the followingpotential advantages. Shutter assemblies incorporating shutters havingboth front and rear obstructing levels provide improved light managementcapabilities. By positioning light obstructing levels in close proximityto apertures formed in light blocking layers located on either side ofthe shutter, the shutter can effectively prevent undesirable leakage oflight exiting the backlight at low angles with respect to the substrate.The shutter can also effectively reduce ambient light reflections. Theresult of this improved light management is an enhanced display contrastratio.

In addition, in some implementations, the process for manufacturing adual-light obstructing level shutter results in some portions of theshutter having a substantially increased thickness in comparison toother portions of the shutter. By positioning such portions directly inthe optical path between apertures defined in the light blocking layers,the shutter can also more effectively obstruct the passage of lightexiting the backlight at angles that are substantially normal to thesubstrate. This can further improve the contrast ratio of the display.

FIG. 1A shows a schematic diagram of an example direct-view MEMS-baseddisplay apparatus 100. The display apparatus 100 includes a plurality oflight modulators 102 a-102 d (generally “light modulators 102”) arrangedin rows and columns. In the display apparatus 100, the light modulators102 a and 102 d are in the open state, allowing light to pass. The lightmodulators 102 b and 102 c are in the closed state, obstructing thepassage of light. By selectively setting the states of the lightmodulators 102 a-102 d, the display apparatus 100 can be utilized toform an image 104 for a backlit display, if illuminated by a lamp orlamps 105. In another implementation, the apparatus 100 may form animage by reflection of ambient light originating from the front of theapparatus. In another implementation, the apparatus 100 may form animage by reflection of light from a lamp or lamps positioned in thefront of the display, i.e., by use of a front light.

In some implementations, each light modulator 102 corresponds to a pixel106 in the image 104. In some other implementations, the displayapparatus 100 may utilize a plurality of light modulators to form apixel 106 in the image 104. For example, the display apparatus 100 mayinclude three color-specific light modulators 102. By selectivelyopening one or more of the color-specific light modulators 102corresponding to a particular pixel 106, the display apparatus 100 cangenerate a color pixel 106 in the image 104. In another example, thedisplay apparatus 100 includes two or more light modulators 102 perpixel 106 to provide luminance level in an image 104. With respect to animage, a “pixel” corresponds to the smallest picture element defined bythe resolution of image. With respect to structural components of thedisplay apparatus 100, the term “pixel” refers to the combinedmechanical and electrical components utilized to modulate the light thatforms a single pixel of the image.

The display apparatus 100 is a direct-view display in that it may notinclude imaging optics typically found in projection applications. In aprojection display, the image formed on the surface of the displayapparatus is projected onto a screen or onto a wall. The displayapparatus is substantially smaller than the projected image. In a directview display, the user sees the image by looking directly at the displayapparatus, which contains the light modulators and optionally abacklight or front light for enhancing brightness and/or contrast seenon the display.

Direct-view displays may operate in either a transmissive or reflectivemode. In a transmissive display, the light modulators filter orselectively block light which originates from a lamp or lamps positionedbehind the display. The light from the lamps is optionally injected intoa lightguide or “backlight” so that each pixel can be uniformlyilluminated. Transmissive direct-view displays are often built ontotransparent or glass substrates to facilitate a sandwich assemblyarrangement where one substrate, containing the light modulators, ispositioned directly on top of the backlight.

Each light modulator 102 can include a shutter 108 and an aperture 109.To illuminate a pixel 106 in the image 104, the shutter 108 ispositioned such that it allows light to pass through the aperture 109towards a viewer. To keep a pixel 106 unlit, the shutter 108 ispositioned such that it obstructs the passage of light through theaperture 109. The aperture 109 is defined by an opening patternedthrough a reflective or light-absorbing material in each light modulator102.

The display apparatus also includes a control matrix connected to thesubstrate and to the light modulators for controlling the movement ofthe shutters. The control matrix includes a series of electricalinterconnects (e.g., interconnects 110, 112 and 114), including at leastone write-enable interconnect 110 (also referred to as a “scan-lineinterconnect”) per row of pixels, one data interconnect 112 for eachcolumn of pixels, and one common interconnect 114 providing a commonvoltage to all pixels, or at least to pixels from both multiple columnsand multiples rows in the display apparatus 100. In response to theapplication of an appropriate voltage (the “write-enabling voltage,VWE”), the write-enable interconnect 110 for a given row of pixelsprepares the pixels in the row to accept new shutter movementinstructions. The data interconnects 112 communicate the new movementinstructions in the form of data voltage pulses. The data voltage pulsesapplied to the data interconnects 112, in some implementations, directlycontribute to an electrostatic movement of the shutters. In some otherimplementations, the data voltage pulses control switches, e.g.,transistors or other non-linear circuit elements that control theapplication of separate actuation voltages, which are typically higherin magnitude than the data voltages, to the light modulators 102. Theapplication of these actuation voltages then results in theelectrostatic driven movement of the shutters 108.

FIG. 1B shows a block diagram of an example host device 120 (i.e., cellphone, smart phone, PDA, MP3 player, tablet, e-reader, netbook,notebook, etc.). The host device 120 includes a display apparatus 128, ahost processor 122, environmental sensors 124, a user input module 126,and a power source.

The display apparatus 128 includes a plurality of scan drivers 130 (alsoreferred to as “write enabling voltage sources”), a plurality of datadrivers 132 (also referred to as “data voltage sources”), a controller134, common drivers 138, lamps 140-146, lamp drivers 148 and an array150 of display elements, such as the light modulators 102 shown in FIG.1A. The scan drivers 130 apply write enabling voltages to scan-lineinterconnects 110. The data drivers 132 apply data voltages to the datainterconnects 112.

In some implementations of the display apparatus, the data drivers 132are configured to provide analog data voltages to the array 150 ofdisplay elements, especially where the luminance level of the image 104is to be derived in analog fashion. In analog operation, the lightmodulators 102 are designed such that when a range of intermediatevoltages is applied through the data interconnects 112, there results arange of intermediate open states in the shutters 108 and therefore arange of intermediate illumination states or luminance levels in theimage 104. In other cases, the data drivers 132 are configured to applyonly a reduced set of 2, 3 or 4 digital voltage levels to the datainterconnects 112. These voltage levels are designed to set, in digitalfashion, an open state, a closed state, or other discrete state to eachof the shutters 108.

The scan drivers 130 and the data drivers 132 are connected to a digitalcontroller circuit 134 (also referred to as the “controller 134”). Thecontroller sends data to the data drivers 132 in a mostly serialfashion, organized in predetermined sequences grouped by rows and byimage frames. The data drivers 132 can include series to parallel dataconverters, level shifting, and for some applications digital to analogvoltage converters.

The display apparatus optionally includes a set of common drivers 138,also referred to as common voltage sources. In some implementations, thecommon drivers 138 provide a DC common potential to all display elementswithin the array 150 of display elements, for instance by supplyingvoltage to a series of common interconnects 114. In some otherimplementations, the common drivers 138, following commands from thecontroller 134, issue voltage pulses or signals to the array 150 ofdisplay elements, for instance global actuation pulses which are capableof driving and/or initiating simultaneous actuation of all displayelements in multiple rows and columns of the array 150.

All of the drivers (e.g., scan drivers 130, data drivers 132 and commondrivers 138) for different display functions are time-synchronized bythe controller 134. Timing commands from the controller coordinate theillumination of red, green and blue and white lamps (140, 142, 144 and146 respectively) via lamp drivers 148, the write-enabling andsequencing of specific rows within the array 150 of display elements,the output of voltages from the data drivers 132, and the output ofvoltages that provide for display element actuation. In someimplementations, the lamps are light emitting diodes (LEDs).

The controller 134 determines the sequencing or addressing scheme bywhich each of the shutters 108 can be re-set to the illumination levelsappropriate to a new image 104. New images 104 can be set at periodicintervals. For instance, for video displays, the color images 104 orframes of video are refreshed at frequencies ranging from 10 to 300Hertz (Hz). In some implementations the setting of an image frame to thearray 150 is synchronized with the illumination of the lamps 140, 142,144 and 146 such that alternate image frames are illuminated with analternating series of colors, such as red, green, and blue. The imageframes for each respective color is referred to as a color subframe. Inthis method, referred to as the field sequential color method, if thecolor subframes are alternated at frequencies in excess of 20 Hz, thehuman brain will average the alternating frame images into theperception of an image having a broad and continuous range of colors. Inalternate implementations, four or more lamps with primary colors can beemployed in display apparatus 100, employing primaries other than red,green, and blue.

In some implementations, where the display apparatus 100 is designed forthe digital switching of shutters 108 between open and closed states,the controller 134 forms an image by the method of time division grayscale, as previously described. In some other implementations, thedisplay apparatus 100 can provide gray scale through the use of multipleshutters 108 per pixel.

In some implementations, the data for an image state 104 is loaded bythe controller 134 to the display element array 150 by a sequentialaddressing of individual rows, also referred to as scan lines. For eachrow or scan line in the sequence, the scan driver 130 applies awrite-enable voltage to the write enable interconnect 110 for that rowof the array 150, and subsequently the data driver 132 supplies datavoltages, corresponding to desired shutter states, for each column inthe selected row. This process repeats until data has been loaded forall rows in the array 150. In some implementations, the sequence ofselected rows for data loading is linear, proceeding from top to bottomin the array 150. In some other implementations, the sequence ofselected rows is pseudo-randomized, in order to minimize visualartifacts. And in some other implementations the sequencing is organizedby blocks, where, for a block, the data for only a certain fraction ofthe image state 104 is loaded to the array 150, for instance byaddressing only every 5th row of the array 150 in sequence.

In some implementations, the process for loading image data to the array150 is separated in time from the process of actuating the displayelements in the array 150. In these implementations, the display elementarray 150 may include data memory elements for each display element inthe array 150 and the control matrix may include a global actuationinterconnect for carrying trigger signals, from common driver 138, toinitiate simultaneous actuation of shutters 108 according to data storedin the memory elements.

In alternative implementations, the array 150 of display elements andthe control matrix that controls the display elements may be arranged inconfigurations other than rectangular rows and columns. For example, thedisplay elements can be arranged in hexagonal arrays or curvilinear rowsand columns. In general, as used herein, the term scan-line shall referto any plurality of display elements that share a write-enablinginterconnect.

The host processor 122 generally controls the operations of the host.For example, the host processor 122 may be a general or special purposeprocessor for controlling a portable electronic device. With respect tothe display apparatus 128, included within the host device 120, the hostprocessor 122 outputs image data as well as additional data about thehost. Such information may include data from environmental sensors, suchas ambient light or temperature; information about the host, including,for example, an operating mode of the host or the amount of powerremaining in the host's power source; information about the content ofthe image data; information about the type of image data; and/orinstructions for display apparatus for use in selecting an imaging mode.

The user input module 126 conveys the personal preferences of the userto the controller 134, either directly, or via the host processor 122.In some implementations, the user input module 126 is controlled bysoftware in which the user programs personal preferences such as “deepercolor,” “better contrast,” “lower power,” “increased brightness,”“sports,” “live action,” or “animation.” In some other implementations,these preferences are input to the host using hardware, such as a switchor dial. The plurality of data inputs to the controller 134 direct thecontroller to provide data to the various drivers 130, 132, 138 and 148which correspond to optimal imaging characteristics.

An environmental sensor module 124 also can be included as part of thehost device 120. The environmental sensor module 124 receives data aboutthe ambient environment, such as temperature and/or ambient lightingconditions. The sensor module 124 can be programmed to distinguishwhether the device is operating in an indoor or office environmentversus an outdoor environment in bright daylight versus an outdoorenvironment at nighttime. The sensor module 124 communicates thisinformation to the display controller 134, so that the controller 134can optimize the viewing conditions in response to the ambientenvironment.

FIG. 2 shows a perspective view of an example shutter-based lightmodulator 200. The shutter-based light modulator 200 is suitable forincorporation into the direct-view MEMS-based display apparatus 100 ofFIG. 1A. The light modulator 200 includes a shutter 202 coupled to anactuator 204. The actuator 204 can be formed from two separate compliantelectrode beam actuators 205 (the “actuators 205”). The shutter 202couples on one side to the actuators 205. The actuators 205 move theshutter 202 transversely over a surface 203 in a plane of motion whichis substantially parallel to the surface 203. The opposite side of theshutter 202 couples to a spring 207 which provides a restoring forceopposing the forces exerted by the actuator 204.

Each actuator 205 includes a compliant load beam 206 connecting theshutter 202 to a load anchor 208. The load anchors 208 along with thecompliant load beams 206 serve as mechanical supports, keeping theshutter 202 suspended proximate to the surface 203. The surface 203includes one or more aperture holes 211 for admitting the passage oflight. The load anchors 208 physically connect the compliant load beams206 and the shutter 202 to the surface 203 and electrically connect theload beams 206 to a bias voltage, in some instances, ground.

If the substrate is opaque, such as silicon, then aperture holes 211 areformed in the substrate by etching an array of holes through thesubstrate. If the substrate is transparent, such as glass or plastic,then the aperture holes 211 are formed in a layer of light-blockingmaterial deposited on the substrate. The aperture holes 211 can begenerally circular, elliptical, polygonal, serpentine, or irregular inshape.

Each actuator 205 also includes a compliant drive beam 216 positionedadjacent to each load beam 206. The drive beams 216 couple at one end toa drive beam anchor 218 shared between the drive beams 216. The otherend of each drive beam 216 is free to move. Each drive beam 216 iscurved such that it is closest to the load beam 206 near the free end ofthe drive beam 216 and the anchored end of the load beam 206.

In operation, a display apparatus incorporating the light modulator 200applies an electric potential to the drive beams 216 via the drive beamanchor 218. A second electric potential may be applied to the load beams206. The resulting potential difference between the drive beams 216 andthe load beams 206 pulls the free ends of the drive beams 216 towardsthe anchored ends of the load beams 206, and pulls the shutter ends ofthe load beams 206 toward the anchored ends of the drive beams 216,thereby driving the shutter 202 transversely toward the drive anchor218. The compliant members 206 act as springs, such that when thevoltage across the beams 206 and 216 potential is removed, the loadbeams 206 push the shutter 202 back into its initial position, releasingthe stress stored in the load beams 206.

A light modulator, such as the light modulator 200, incorporates apassive restoring force, such as a spring, for returning a shutter toits rest position after voltages have been removed. Other shutterassemblies can incorporate a dual set of “open” and “closed” actuatorsand separate sets of “open” and “closed” electrodes for moving theshutter into either an open or a closed state.

There are a variety of methods by which an array of shutters andapertures can be controlled via a control matrix to produce images, inmany cases moving images, with appropriate luminance levels. In somecases, control is accomplished by means of a passive matrix array of rowand column interconnects connected to driver circuits on the peripheryof the display. In other cases, it is appropriate to include switchingand/or data storage elements within each pixel of the array (theso-called active matrix) to improve the speed, the luminance leveland/or the power dissipation performance of the display.

FIG. 3A shows a schematic diagram of an example control matrix 300. Thecontrol matrix 300 is suitable for controlling the light modulatorsincorporated into the MEMS-based display apparatus 100 of FIG. 1A. FIG.3B shows a perspective view of an example array 320 of shutter-basedlight modulators connected to the control matrix 300 of FIG. 3A. Thecontrol matrix 300 may address an array of pixels 320 (the “array 320”).Each pixel 301 can include an elastic shutter assembly 302, such as theshutter assembly 200 of FIG. 2, controlled by an actuator 303. Eachpixel also can include an aperture layer 322 that includes apertures324.

The control matrix 300 is fabricated as a diffused orthin-film-deposited electrical circuit on the surface of a substrate 304on which the shutter assemblies 302 are formed. The control matrix 300includes a scan-line interconnect 306 for each row of pixels 301 in thecontrol matrix 300 and a data-interconnect 308 for each column of pixels301 in the control matrix 300. Each scan-line interconnect 306electrically connects a write-enabling voltage source 307 to the pixels301 in a corresponding row of pixels 301. Each data interconnect 308electrically connects a data voltage source 309 (“Vd source”) to thepixels 301 in a corresponding column of pixels. In the control matrix300, the Vd source 309 provides the majority of the energy to be usedfor actuation of the shutter assemblies 302. Thus, the data voltagesource, Vd source 309, also serves as an actuation voltage source.

Referring to FIGS. 3A and 3B, for each pixel 301 or for each shutterassembly 302 in the array of pixels 320, the control matrix 300 includesa transistor 310 and a capacitor 312. The gate of each transistor 310 iselectrically connected to the scan-line interconnect 306 of the row inthe array 320 in which the pixel 301 is located. The source of eachtransistor 310 is electrically connected to its corresponding datainterconnect 308. The actuators 303 of each shutter assembly 302 includetwo electrodes. The drain of each transistor 310 is electricallyconnected in parallel to one electrode of the corresponding capacitor312 and to one of the electrodes of the corresponding actuator 303. Theother electrode of the capacitor 312 and the other electrode of theactuator 303 in shutter assembly 302 are connected to a common or groundpotential. In alternate implementations, the transistors 310 can bereplaced with semiconductor diodes and/or metal-insulator-metal sandwichtype switching elements.

In operation, to form an image, the control matrix 300 write-enableseach row in the array 320 in a sequence by applying Vwe to eachscan-line interconnect 306 in turn. For a write-enabled row, theapplication of Vwe to the gates of the transistors 310 of the pixels 301in the row allows the flow of current through the data interconnects 308through the transistors 310 to apply a potential to the actuator 303 ofthe shutter assembly 302. While the row is write-enabled, data voltagesVd are selectively applied to the data interconnects 308. Inimplementations providing analog gray scale, the data voltage applied toeach data interconnect 308 is varied in relation to the desiredbrightness of the pixel 301 located at the intersection of thewrite-enabled scan-line interconnect 306 and the data interconnect 308.In implementations providing digital control schemes, the data voltageis selected to be either a relatively low magnitude voltage (i.e., avoltage near ground) or to meet or exceed Vat (the actuation thresholdvoltage). In response to the application of Vat to a data interconnect308, the actuator 303 in the corresponding shutter assembly actuates,opening the shutter in that shutter assembly 302. The voltage applied tothe data interconnect 308 remains stored in the capacitor 312 of thepixel 301 even after the control matrix 300 ceases to apply Vwe to arow. Therefore, the voltage Vwe does not have to wait and hold on a rowfor times long enough for the shutter assembly 302 to actuate; suchactuation can proceed after the write-enabling voltage has been removedfrom the row. The capacitors 312 also function as memory elements withinthe array 320, storing actuation instructions for the illumination of animage frame.

The pixels 301 as well as the control matrix 300 of the array 320 areformed on a substrate 304. The array 320 includes an aperture layer 322,disposed on the substrate 304, which includes a set of apertures 324 forrespective pixels 301 in the array 320. The apertures 324 are alignedwith the shutter assemblies 302 in each pixel. In some implementations,the substrate 304 is made of a transparent material, such as glass orplastic. In some other implementations, the substrate 304 is made of anopaque material, but in which holes are etched to form the apertures324.

The shutter assembly 302 together with the actuator 303 can be madebi-stable. That is, the shutters can exist in at least two equilibriumpositions (e.g., open or closed) with little or no power required tohold them in either position. More particularly, the shutter assembly302 can be mechanically bi-stable. Once the shutter of the shutterassembly 302 is set in position, no electrical energy or holding voltageis required to maintain that position. The mechanical stresses on thephysical elements of the shutter assembly 302 can hold the shutter inplace.

The shutter assembly 302 together with the actuator 303 also can be madeelectrically bi-stable. In an electrically bi-stable shutter assembly,there exists a range of voltages below the actuation voltage of theshutter assembly, which if applied to a closed actuator (with theshutter being either open or closed), holds the actuator closed and theshutter in position, even if an opposing force is exerted on theshutter. The opposing force may be exerted by a spring such as thespring 207 in the shutter-based light modulator 200 depicted in FIG. 2,or the opposing force may be exerted by an opposing actuator, such as an“open” or “closed” actuator.

The light modulator array 320 is depicted as having a single MEMS lightmodulator per pixel. Other implementations are possible in whichmultiple MEMS light modulators are provided in each pixel, therebyproviding the possibility of more than just binary “on” or “off” opticalstates in each pixel. Certain forms of coded area division gray scaleare possible where multiple MEMS light modulators in the pixel areprovided, and where apertures 324, which are associated with each of thelight modulators, have unequal areas.

FIGS. 4A and 4B show views of an example dual actuator shutter assembly400. The dual actuator shutter assembly 400, as depicted in FIG. 4A, isin an open state. FIG. 4B shows the dual actuator shutter assembly 400in a closed state. In contrast to the shutter assembly 200, the shutterassembly 400 includes actuators 402 and 404 on either side of a shutter406. Each actuator 402 and 404 is independently controlled. A firstactuator, a shutter-open actuator 402, serves to open the shutter 406. Asecond opposing actuator, the shutter-close actuator 404, serves toclose the shutter 406. Both of the actuators 402 and 404 are compliantbeam electrode actuators. The actuators 402 and 404 open and close theshutter 406 by driving the shutter 406 substantially in a plane parallelto an aperture layer 407 over which the shutter is suspended. Theshutter 406 is suspended a short distance over the aperture layer 407 byanchors 408 attached to the actuators 402 and 404. The inclusion ofsupports attached to both ends of the shutter 406 along its axis ofmovement reduces out of plane motion of the shutter 406 and confines themotion substantially to a plane parallel to the substrate. By analogy tothe control matrix 300 of FIG. 3A, a control matrix suitable for usewith the shutter assembly 400 might include one transistor and onecapacitor for each of the opposing shutter-open and shutter-closeactuators 402 and 404.

The shutter 406 includes two shutter apertures 412 through which lightcan pass. The aperture layer 407 includes a set of three apertures 409.In FIG. 4A, the shutter assembly 400 is in the open state and, as such,the shutter-open actuator 402 has been actuated, the shutter-closeactuator 404 is in its relaxed position, and the centerlines of theshutter apertures 412 coincide with the centerlines of two of theaperture layer apertures 409. In FIG. 4B, the shutter assembly 400 hasbeen moved to the closed state and, as such, the shutter-open actuator402 is in its relaxed position, the shutter-close actuator 404 has beenactuated, and the light blocking portions of the shutter 406 are now inposition to block transmission of light through the apertures 409(depicted as dotted lines).

Each aperture has at least one edge around its periphery. For example,the rectangular apertures 409 have four edges. In alternativeimplementations in which circular, elliptical, oval, or other curvedapertures are formed in the aperture layer 407, each aperture may haveonly a single edge. In some other implementations, the apertures neednot be separated or disjoint in the mathematical sense, but instead canbe connected. That is to say, while portions or shaped sections of theaperture may maintain a correspondence to each shutter, several of thesesections may be connected such that a single continuous perimeter of theaperture is shared by multiple shutters.

In order to allow light with a variety of exit angles to pass throughapertures 412 and 409 in the open state, it is advantageous to provide awidth or size for shutter apertures 412 which is larger than acorresponding width or size of apertures 409 in the aperture layer 407.In order to effectively block light from escaping in the closed state,it is preferable that the light blocking portions of the shutter 406overlap the apertures 409. FIG. 4B shows a predefined overlap 416between the edge of light blocking portions in the shutter 406 and oneedge of the aperture 409 formed in the aperture layer 407.

The electrostatic actuators 402 and 404 are designed so that theirvoltage-displacement behavior provides a bi-stable characteristic to theshutter assembly 400. For each of the shutter-open and shutter-closeactuators there exists a range of voltages below the actuation voltage,which if applied while that actuator is in the closed state (with theshutter being either open or closed), will hold the actuator closed andthe shutter in position, even after an actuation voltage is applied tothe opposing actuator. The minimum voltage needed to maintain ashutter's position against such an opposing force is referred to as amaintenance voltage Vm.

FIG. 5 shows a cross sectional view of an example display apparatus 500incorporating shutter-based light modulators (shutter assemblies) 502.Each shutter assembly 502 incorporates a shutter 503 and an anchor 505.Not shown are the compliant beam actuators which, when connected betweenthe anchors 505 and the shutters 503, help to suspend the shutters 503 ashort distance above the surface. The shutter assemblies 502 aredisposed on a transparent substrate 504, such a substrate made ofplastic or glass. A rear-facing reflective layer, reflective film 506,disposed on the substrate 504 defines a plurality of surface apertures508 located beneath the closed positions of the shutters 503 of theshutter assemblies 502. The reflective film 506 reflects light notpassing through the surface apertures 508 back towards the rear of thedisplay apparatus 500. The reflective aperture layer 506 can be afine-grained metal film without inclusions formed in thin film fashionby a number of vapor deposition techniques including sputtering,evaporation, ion plating, laser ablation, or chemical vapor deposition(CVD). In some other implementations, the rear-facing reflective layer506 can be formed from a mirror, such as a dielectric mirror. Adielectric mirror can be fabricated as a stack of dielectric thin filmswhich alternate between materials of high and low refractive index. Thevertical gap which separates the shutters 503 from the reflective film506, within which the shutter is free to move, is in the range of 0.5 to10 microns. The magnitude of the vertical gap is preferably less thanthe lateral overlap between the edge of shutters 503 and the edge ofapertures 508 in the closed state, such as the overlap 416 depicted inFIG. 4B.

The display apparatus 500 includes an optional diffuser 512 and/or anoptional brightness enhancing film 514 which separate the substrate 504from a planar light guide 516. The light guide 516 includes atransparent, i.e., glass or plastic material. The light guide 516 isilluminated by one or more light sources 518, forming a backlight 515.The light sources 518 can be, for example, and without limitation,incandescent lamps, fluorescent lamps, lasers or light emitting diodes(LEDs). A reflector 519 helps direct light from lamp 518 towards thelight guide 516. A front-facing reflective film 520 is disposed behindthe light guide 516, reflecting light towards the shutter assemblies502. Light rays such as ray 521 from the backlight that do not passthrough one of the shutter assemblies 502 will be returned to thebacklight 515 and reflected again from the film 520. In this fashionlight that fails to leave the display apparatus 500 to form an image onthe first pass can be recycled and made available for transmissionthrough other open apertures in the array of shutter assemblies 502.Such light recycling has been shown to increase the illuminationefficiency of the display.

The light guide 516 includes a set of geometric light redirectors orprisms 517 which re-direct light from the lamps 518 towards theapertures 508 and hence toward the front of the display. The lightredirectors 517 can be molded into the plastic body of light guide 516with shapes that can be alternately triangular, trapezoidal, or curvedin cross section. The density of the prisms 517 generally increases withdistance from the lamp 518.

In some implementations, the aperture layer 506 can be made of a lightabsorbing material, and in alternate implementations the surfaces ofshutter 503 can be coated with either a light absorbing or a lightreflecting material. In some other implementations, the aperture layer506 can be deposited directly on the surface of the light guide 516. Insome implementations, the aperture layer 506 need not be disposed on thesame substrate as the shutters 503 and anchors 505 (such as in theMEMS-down configuration described below).

In some implementations, the light sources 518 can include lamps ofdifferent colors, for instance, the colors red, green and blue. A colorimage can be formed by sequentially illuminating images with lamps ofdifferent colors at a rate sufficient for the human brain to average thedifferent colored images into a single multi-color image. The variouscolor-specific images are formed using the array of shutter assemblies502. In another implementation, the light source 518 includes lampshaving more than three different colors. For example, the light source518 may have red, green, blue and white lamps, or red, green, blue andyellow lamps. In some other implementations, the light source 518 mayinclude cyan, magenta, yellow and white lamps, red, green, blue andwhite lamps. In some other implementations, additional lamps may beincluded in the light source 518. For example, if using five colors, thelight source 518 may include red, green, blue, cyan and yellow lamps. Insome other implementations, the light source 518 may include white,orange, blue, purple and green lamps or white, blue, yellow, red andcyan lamps. If using six colors, the light source 518 may include red,green, blue, cyan, magenta and yellow lamps or white, cyan, magenta,yellow, orange and green lamps.

A cover plate 522 forms the front of the display apparatus 500. The rearside of the cover plate 522 can be covered with a black matrix 524 toincrease contrast. In alternate implementations the cover plate includescolor filters, for instance distinct red, green, and blue filterscorresponding to different ones of the shutter assemblies 502. The coverplate 522 is supported a predetermined distance away from the shutterassemblies 502 forming a gap 526. The gap 526 is maintained bymechanical supports or spacers 527 and/or by an adhesive seal 528attaching the cover plate 522 to the substrate 504.

The adhesive seal 528 seals in a fluid 530. The fluid 530 is engineeredwith viscosities preferably below about 10 centipoise and with relativedielectric constant preferably above about 2.0, and dielectric breakdownstrengths above about 104 V/cm. The fluid 530 also can serve as alubricant. In some implementations, the fluid 530 is a hydrophobicliquid with a high surface wetting capability. In alternateimplementations, the fluid 530 has a refractive index that is eithergreater than or less than that of the substrate 504.

Displays that incorporate mechanical light modulators can includehundreds, thousands, or in some cases, millions of moving elements. Insome devices, every movement of an element provides an opportunity forstatic friction to disable one or more of the elements. This movement isfacilitated by immersing all the parts in a fluid (also referred to asfluid 530) and sealing the fluid (e.g., with an adhesive) within a fluidspace or gap in a MEMS display cell. The fluid 530 is usually one with alow coefficient of friction, low viscosity, and minimal degradationeffects over the long term. When the MEMS-based display assemblyincludes a liquid for the fluid 530, the liquid at least partiallysurrounds some of the moving parts of the MEMS-based light modulator. Insome implementations, in order to reduce the actuation voltages, theliquid has a viscosity below 70 centipoise. In some otherimplementations, the liquid has a viscosity below 10 centipoise. Liquidswith viscosities below 70 centipoise can include materials with lowmolecular weights: below 4000 grams/mole, or in some cases below 400grams/mole. Fluids 530 that also may be suitable for suchimplementations include, without limitation, de-ionized water, methanol,ethanol and other alcohols, paraffins, olefins, ethers, silicone oils,fluorinated silicone oils, or other natural or synthetic solvents orlubricants. Useful fluids can be polydimethylsiloxanes (PDMS), such ashexamethyldisiloxane and octamethyltrisiloxane, or alkyl methylsiloxanes such as hexylpentamethyldisiloxane. Useful fluids can bealkanes, such as octane or decane. Useful fluids can be nitroalkanes,such as nitromethane. Useful fluids can be aromatic compounds, such astoluene or diethylbenzene. Useful fluids can be ketones, such asbutanone or methyl isobutyl ketone. Useful fluids can be chlorocarbons,such as chlorobenzene. Useful fluids can be chlorofluorocarbons, such asdichlorofluoroethane or chlorotrifluoroethylene. Other fluids consideredfor these display assemblies include butyl acetate anddimethylformamide. Still other useful fluids for these displays includehydro fluoro ethers, perfluoropolyethers, hydro fluoro poly ethers,pentanol, and butanol. Example suitable hydro fluoro ethers includeethyl nonafluorobutyl ether and2-trifluoromethyl-3-ethoxydodecafluorohexane.

A sheet metal or molded plastic assembly bracket 532 holds the coverplate 522, the substrate 504, the backlight and the other componentparts together around the edges. The assembly bracket 532 is fastenedwith screws or indent tabs to add rigidity to the combined displayapparatus 500. In some implementations, the light source 518 is moldedin place by an epoxy potting compound. Reflectors 536 help return lightescaping from the edges of the light guide 516 back into the light guide516. Not depicted in FIG. 5 are electrical interconnects which providecontrol signals as well as power to the shutter assemblies 502 and thelamps 518.

The display apparatus 500 is referred to as the MEMS-up configuration,wherein the MEMS based light modulators are formed on a front surface ofthe substrate 504, i.e., the surface that faces toward the viewer. Theshutter assemblies 502 are built directly on top of the reflectiveaperture layer 506. In an alternate implementation, referred to as theMEMS-down configuration, the shutter assemblies are disposed on asubstrate separate from the substrate on which the reflective aperturelayer is formed. The substrate on which the reflective aperture layer isformed, defining a plurality of apertures, is referred to herein as theaperture plate. In the MEMS-down configuration, the substrate thatcarries the MEMS-based light modulators takes the place of the coverplate 522 in the display apparatus 500 and is oriented such that theMEMS-based light modulators are positioned on the rear surface of thetop substrate, i.e., the surface that faces away from the viewer andtoward the light guide 516. The MEMS-based light modulators are therebypositioned directly opposite to and across a gap from the reflectiveaperture layer 506. The gap can be maintained by a series of spacerposts connecting the aperture plate and the substrate on which the MEMSmodulators are formed. In some implementations, the spacers are disposedwithin or between each pixel in the array. The gap or distance thatseparates the MEMS light modulators from their corresponding aperturesis preferably less than 10 microns, or a distance that is less than theoverlap between shutters and apertures, such as overlap 416.

FIGS. 6A-6E show cross sectional views of stages of construction of anexample composite shutter assembly. FIG. 6A shows an example crosssectional diagram of a completed composite shutter assembly 600. Theshutter assembly 600 includes a shutter 601, two compliant beams 602,and an anchor structure 604 built-up on a substrate 603 and an aperturelayer 606. The elements of the composite shutter assembly 600 include afirst mechanical layer 605, a conductor layer 607, a second mechanicallayer 609, and an encapsulating dielectric 611. At least one of themechanical layers 605 or 609 can be deposited to thicknesses in excessof 0.15 microns, as one or both of the mechanical layers 605 or 609serves as the principal load bearing and mechanical actuation member forthe shutter assembly 600, though in some implementations, the mechanicallayers 605 and 609 may be thinner. Candidate materials for themechanical layers 605 and 609 include, without limitation, metals suchas aluminum (Al), copper (Cu), nickel (Ni), chromium (Cr), molybdenum(Mo), titanium (Ti), tantalum (Ta), niobium (Nb), neodymium (Nd), oralloys thereof; dielectric materials such as aluminum oxide (Al2O3),silicon oxide (SiO2), tantalum pentoxide (Ta2O5), or silicon nitride(Si3N4); or semiconducting materials such as diamond-like carbon,silicon (Si), germanium (Ge), gallium arsenide (GaAs), cadmium telluride(CdTe) or alloys thereof. At least one of the layers, such as theconductor layer 607, should be electrically conducting so as to carrycharge on to and off of the actuation elements. Candidate materialsinclude, without limitation, Al, Cu, Ni, Cr, Mo, Ti, Ta, Nb, Nd, oralloys thereof or semiconducting materials such as diamond-like carbon,Si, Ge, GaAs, CdTe or alloys thereof. In some implementations employingsemiconductor layers, the semiconductors are doped with impurities suchas phosphorus (P), arsenic (As), boron (B), or Al. FIG. 6A depicts asandwich configuration for the composite in which the mechanical layers605 and 609, having similar thicknesses and mechanical properties, aredeposited on either side of the conductor layer 607. In someimplementations, the sandwich structure helps to ensure that stressesremaining after deposition and/or stresses that are imposed bytemperature variations will not act to cause bending, warping or otherdeformation of the shutter assembly 600.

In some implementations, the order of the layers in the compositeshutter assembly 600 can be inverted, such that the outside of theshutter assembly 600 is formed from a conductor layer while the insideof the shutter assembly 600 is formed from a mechanical layer.

The shutter assembly 600 can include an encapsulating dielectric 611. Insome implementations, dielectric coatings can be applied in conformalfashion, such that all exposed bottom, top, and side surfaces of theshutter 601, the anchor 604, and the beams 602 are uniformly coated.Such thin films can be grown by thermal oxidation and/or by conformalCVD of an insulator such as Al2O3, chromium (III) oxide (Cr2O3),titanium oxide (TiO2), hafnium oxide (HfO2), vanadium oxide (V2O5),niobium oxide (Nb2O5), Ta2O5, SiO2, or Si3N4, or by depositing similarmaterials via atomic layer deposition. The dielectric coating layer canbe applied with thicknesses in the range of 10 nm to 1 micron. In someimplementations, sputtering and evaporation can be used to deposit thedielectric coating onto sidewalls.

FIGS. 6B-6E show example cross sectional views of the results of certainintermediate manufacturing stages of an example process used to form theshutter assembly 600 depicted in FIG. 6A. In some implementations, theshutter assembly 600 is built on top of a pre-existing control matrix,such as an active matrix array of thin film transistors, such as thecontrol matrices depicted in FIGS. 3A and 3B.

FIG. 6B shows a cross sectional view of the results of a first stage inan example process of forming the shutter assembly 600. As depicted inFIG. 6B, a sacrificial layer 613 is deposited and patterned. In someimplementations, polyimide is used as a sacrificial layer material.Other candidate sacrificial layer materials include, without limitation,polymer materials such as polyamide, fluoropolymer, benzocyclobutene,polyphenylquinoxylene, parylene, or polynorbornene. These materials arechosen for their ability to planarize rough surfaces, maintainmechanical integrity at processing temperatures in excess of 250° C.,and their ease of etch and/or thermal decomposition during removal. Inother implementations, the sacrificial layer 613 is formed from aphotoresist, such as polyvinyl acetate, polyvinyl ethylene, and phenolicor novolac resins. An alternate sacrificial layer material used in someimplementations is SiO2, which can be removed preferentially as long asother electronic or structural layers are resistant to the hydrofluoricacid solutions used for its removal. One such suitable resistantmaterial is Si3N4. Another alternate sacrificial layer material is Si,which can be removed preferentially as long as electronic or structurallayers are resistant to the fluorine plasmas or xenon difluoride (XeF2)used for its removal, such as most metals and Si3N4. Yet anotheralternate sacrificial layer material is Al, which can be removedpreferentially as long as other electronic or structural layers areresistant to strong base solutions, such as concentrated sodiumhydroxide (NaOH) solutions. Suitable materials include, for example, Cr,Ni, Mo, Ta and Si. Still another alternate sacrificial layer material isCu, which can be removed preferentially as long as other electronic orstructural layers are resistant to nitric or sulfuric acid solutions.Such materials include, for example, Cr, Ni, and Si.

Next the sacrificial layer 613 is patterned to expose holes or vias atthe anchor regions 604. In implementations employing polyimide or othernon-photoactive materials as the sacrificial layer material, thesacrificial layer material can be formulated to include photoactiveagents, allowing regions exposed through a UV photomask to bepreferentially removed in a developer solution. Sacrificial layersformed from other materials can be patterned by coating the sacrificiallayer 613 in an additional layer of photoresist, photopatterning thephotoresist, and finally using the photoresist as an etching mask. Thesacrificial layer 613 alternatively can be patterned by coating thesacrificial layer 613 with a hard mask, which can be a thin layer ofSiO2 or a metal such as Cr. A photopattern is then transferred to thehard mask by way of photoresist and wet chemical etching. The patterndeveloped in the hard mask can be resistant to dry chemical,anisotropic, or plasma etching—techniques which can be used to impartdeep and narrow anchor holes into the sacrificial layer 613.

After the anchor regions 604 have been opened in the sacrificial layer613, the exposed and underlying conducting surface 614 can be etched,either chemically or via the sputtering effects of a plasma, to removeany surface oxide layers. Such a contact etching stage can improve theohmic contact between the underlying conducting surface 614 and theshutter material. After patterning of the sacrificial layer 613, anyphotoresist layers or hard masks can be removed through use of eithersolvent cleaning or acid etching.

Next, in the process for building the shutter assembly 600, as depictedin FIG. 6C, the shutter materials are deposited. The shutter assembly600 is composed of multiple thin films: the first mechanical layer 605,the conductor layer 607 and the second mechanical layer 609. In someimplementations, the first mechanical layer 605 is an amorphous silicon(a-Si) layer, the conductor layer 607 is Al and the second mechanicallayer 609 is a-Si. The first mechanical layer 605, the conductor layer607, and the second mechanical layer 609 are deposited at a temperaturewhich is below that at which physical degradation occurs for thesacrificial layer 613. For instance, polyimide decomposes attemperatures above about 400° C. Therefore, in some implementations, thefirst mechanical layer 605, the conductor layer 607 and the secondmechanical layer 609 are deposited at temperatures below about 400° C.,allowing usage of polyimide as a sacrificial layer material. In someimplementations, hydrogenated amorphous silicon (a-Si:H) is a usefulmechanical material for the first and second mechanical layers 605 and609 since it can be grown to thicknesses in the range of about 0.15 toabout 3 microns, in a relatively stress-free state, by way ofplasma-enhanced chemical vapor deposition (PECVD) from silane gas attemperatures in the range of about 250 to about 350° C. In some of suchimplementations, phosphine gas (PH3) is used as a dopant so that thea-Si can be grown with resistivities below about 1 ohm-cm. In alternateimplementations, a similar PECVD technique can be used for thedeposition of Si3N4, silicon-rich Si3N4, or SiO2 materials as the firstmechanical layer 605 or for the deposition of diamond-like carbon, Ge,SiGe, CdTe, or other semiconducting materials for the first mechanicallayer 605. An advantage of the PECVD deposition technique is that thedeposition can be quite conformal, that is, it can coat a variety ofinclined surfaces or the inside surfaces of narrow via holes. Even ifthe anchor or via holes which are cut into the sacrificial layermaterial present nearly vertical sidewalls, the PECVD technique canprovide a substantially continuous coating between the bottom and tophorizontal surfaces of the anchor.

In addition to the PECVD technique, alternate suitable techniquesavailable for the growth of the first and second mechanical layers 605and 609 include RF or DC sputtering, metal-organic CVD, evaporation,electroplating or electroless plating.

For the conductor layer 607, in some implementations, a metal thin film,such as Al, is utilized. In some other implementations, alternativemetals, such as Cu, Ni, Mo, or Ta can be chosen. The inclusion of such aconducting material serves two purposes. It reduces the overall sheetresistance of the shutter 601, and it helps to block the passage ofvisible light through the shutter 601, since a-Si, if less than about 2microns thick, as may be used in some implementations of the shutter601, can transmit visible light to some degree. The conducting materialcan be deposited either by sputtering or, in a more conformal fashion,by CVD techniques, electroplating, or electroless plating.

FIG. 6D shows the results of the next set of processing stages used inthe formation of the shutter assembly 600. The first mechanical layer605, the conductor layer 607, and the second mechanical layer 609 arephotomasked and etched while the sacrificial layer 613 is still on thesubstrate 603. First, a photoresist material is applied, then exposedthrough a photomask, and then developed to form an etch mask. Amorphoussilicon, Si3N4, and SiO2 can then be etched in fluorine-based plasmachemistries. SiO2 mechanical layers also can be etched using HF wetchemicals; and any metals in the conductor layer 607 can be etched witheither wet chemicals or chlorine-based plasma chemistries.

The pattern shapes applied through the photomask can influence themechanical properties, such as stiffness, compliance, and the voltageresponse in the actuator and shutter 601 of the shutter assembly 600.The shutter assembly 600 includes the compliant beams 602, shown incross section. Each compliant beam 602 is shaped such that the width isless than the total height or thickness of the shutter material. In someimplementations, the beam dimensional ratio is maintained at about 1.4:1or greater, with the compliant beams 602 being taller or thicker thanthey are wide.

The results of subsequent stages of the example manufacturing processfor building the shutter assembly 600 are depicted in FIG. 6E. Thesacrificial layer 613 is removed, which frees-up all moving parts fromthe substrate 603, except at the anchor points. In some implementations,polyimide sacrificial materials are removed in an oxygen plasma. Otherpolymer materials used for the sacrificial layer 613 also can be removedin an oxygen plasma, or in some cases by thermal pyrolysis. Somesacrificial layer materials (such as SiO2) can be removed by wetchemical etching or by vapor phase etching.

In a final process, the results of which are depicted in FIG. 6A, theencapsulating dielectric 611 is deposited on all exposed surfaces of theshutter assembly 600. In some implementations, the encapsulatingdielectric 611 can be applied in a conformal fashion, such that allbottom, top, and side surfaces of the shutter 601 and the beams 602 areuniformly coated using CVD. In some other implementations, only the topand side surfaces of the shutter 601 are coated. In someimplementations, Al2O3 is used for the encapsulating dielectric 611 andis deposited by atomic layer deposition to thicknesses in the range ofabout 10 to about 100 nanometers.

Finally, anti-stiction coatings can be applied to the surfaces of theshutter 601 and the beams 602. These coatings prevent the unwantedstickiness or adhesion between two independent beams of an actuator.Suitable coatings include carbon films (both graphite and diamond-like)as well as fluoropolymers, and/or low vapor pressure lubricants, as wellas chlorosilanes, hydrocarbon chlorosilanes, fluorocarbon chlorosilanes,such as methoxy-terminated silanes, perfluoronated, amino-silanes,siloxanes and carboxylic acid based monomers and species. These coatingscan be applied by either exposure to a molecular vapor or bydecomposition of precursor compounds by way of CVD. Anti-stictioncoatings also can be created by the chemical alteration of shuttersurfaces, such as by fluoridation, silanization, siloxidation, orhydrogenation of insulating surfaces.

One class of suitable actuators for use in MEMS-based shutter displaysinclude compliant actuator beams for controlling shutter motion that istransverse to or in-the-plane of the display substrate. The voltageemployed for the actuation of such shutter assemblies decreases as theactuator beams become more compliant. The control of actuated motionalso improves if the beams are shaped such that in-plane motion ispreferred or promoted with respect to out-of-plane motion. Thus, in someimplementations, the compliant actuator beams have a rectangular crosssection, such that the beams are taller or thicker than they are wide.

The stiffness of a long rectangular beam with respect to bending withina particular plane scales with the thinnest dimension of that beam inthat plane to the third power. It is therefore advantageous to reducethe width of the compliant beams to reduce the actuation voltages forin-plane motion. When using conventional photolithography equipment todefine and fabricate the shutter and actuator structures, however, theminimum width of the beams can be limited to the resolution of theoptics. And although photolithography equipment has been developed fordefining patterns in photoresist with narrow features, such equipment isexpensive, and the areas over which patterning can be accomplished in asingle exposure are limited. For economical photolithography over largepanels of glass or other transparent substrates, the patterningresolution or minimum feature size is typically limited to severalmicrons.

FIGS. 7A-7D show isometric views of stages of construction of an exampleshutter assembly 700 with narrow sidewall beams. This alternate processyields compliant actuator beams 718 and 720 and a compliant spring beam716 (collectively referred to as “sidewall beams 716, 718 and 720”),which have a width well below the conventional lithography limits onlarge glass panels. In the process depicted in FIGS. 7A-7D, thecompliant beams of shutter assembly 700 are formed as sidewall featureson a mold made from a sacrificial material. The process is referred toas a sidewall beams process.

The process of forming the shutter assembly 700 with the sidewall beams716, 718 and 720 begins, as depicted in FIG. 7A, with the deposition andpatterning of a first sacrificial material 701. The pattern defined inthe first sacrificial material 701 creates openings or vias 702 withinwhich anchors for the shutter assembly 700 eventually will be formed.The deposition and patterning of the first sacrificial material 701 issimilar in concept, and uses similar materials and techniques, as thosedescribed for the deposition and patterning described in relation toFIGS. 6A-6E.

The process of forming the sidewall beams 716, 718 and 720 continueswith the deposition and patterning of a second sacrificial material 705.FIG. 7B shows the shape of a mold 703 that is created after patterningof the second sacrificial material 705. The mold 703 also includes thefirst sacrificial material 701 with its previously defined vias 702. Themold 703 in FIG. 7B includes two distinct horizontal levels. The bottomhorizontal level 708 of the mold 703 is established by the top surfaceof the first sacrificial layer 701 and is accessible in those areaswhere the second sacrificial material 705 has been etched away. The tophorizontal level 710 of the mold 703 is established by the top surfaceof the second sacrificial material 705. The mold 703 depicted in FIG. 7Balso includes substantially vertical sidewalls 709. Materials for use asthe first and second sacrificial materials 701 and 705 are describedabove with respect to the sacrificial layer 613 of FIGS. 6A-6E.

The process of forming the sidewall beams 716, 718 and 720 continueswith the deposition and patterning of shutter material onto all of theexposed surfaces of the sacrificial mold 703, as depicted in FIG. 7C.Suitable materials for use in forming the shutter 712 are describedabove with respect to the first mechanical layer 605, the conductorlayer 607, and the second mechanical layer 609 of FIGS. 6A-6E. Theshutter material is deposited to a thickness of less than about 2microns. In some implementations, the shutter material is deposited tohave a thickness of less than about 1.5 microns. In some otherimplementations, the shutter material is deposited to have a thicknessof less than about 1.0 microns, and as thin as about 0.10 microns. Afterdeposition, the shutter material (which may be a composite of severalmaterials as described above) is patterned, as depicted in FIG. 7C.First, a photoresist is deposited on the shutter material. Thephotoresist is then patterned. The pattern developed into thephotoresist is designed such that the shutter material, after asubsequent etch stage, remains in the region of the shutter 712 as wellas at the anchors 714.

The manufacturing process continues with applying an anisotropic etch,resulting in the structure depicted in FIG. 7C. The anisotropic etch ofthe shutter material is carried out in a plasma atmosphere with avoltage bias applied to the substrate 726 or to an electrode inproximity to the substrate 726. The biased substrate 726 (with electricfield perpendicular to the surface of the substrate 726) leads toacceleration of ions toward the substrate 726 at an angle nearlyperpendicular to the substrate 726. Such accelerated ions, coupled withthe etching chemicals, lead to etch rates that are much faster in adirection that is normal to the plane of the substrate 726 as comparedto directions parallel to the substrate 726. Undercut-etching of shuttermaterial in the regions protected by a photoresist is therebysubstantially eliminated. Along the vertical sidewalls 709 of the mold703, which are substantially parallel to the track of the acceleratedions, the shutter material also is substantially protected from theanisotropic etch. Such protected sidewall shutter material form thesidewall beams 716, 718, and 720 for supporting the shutter 712. Alongother (non-photoresist-protected) horizontal surfaces of the mold 703,such as the top horizontal surface 710 or the bottom horizontal surface708, the shutter material has been substantially completely removed bythe etch.

The anisotropic etch used to form the sidewall beams 716, 718 and 720can be achieved in either an RF or DC plasma etching device as long asprovision for electrical bias of the substrate 726 or of an electrode inclose proximity of the substrate 726 is supplied. For the case of RFplasma etching, an equivalent self-bias can be obtained by disconnectingthe substrate holder from the grounding plates of the excitationcircuit, thereby allowing the substrate potential to float in theplasma. In some implementations, it is possible to provide an etchinggas such as trifluoromethane (CHF3), perfluorobutene (C4F8), orchloroform (CHCl3) in which both carbon and hydrogen and/or carbon andfluorine are constituents in the etch gas. When coupled with adirectional plasma, achieved again through voltage biasing of thesubstrate 726, the liberated carbon (C), hydrogen (H), and/or fluorine(F) atoms can migrate to the vertical sidewalls 709 where they build upa passive or protective quasi-polymer coating. This quasi-polymercoating further protects the sidewall beams 716, 718 and 720 frometching or chemical attack.

The process of forming the sidewall beams 716, 718 and 720 is completedwith the removal of the remainder of the second sacrificial material 705and the first sacrificial material 701. The result is shown in FIG. 7D.The process of removing sacrificial material is similar to thatdescribed with respect to FIG. 6E. The material deposited on thevertical sidewalls 709 of the mold 703 remain as the sidewall beams 716,718 and 720. The sidewall beam 716 serves as a spring mechanicallyconnecting one of the anchors 714 to the shutter 712, and also providesa passive restoring force and to counter the forces applied by theactuator formed from the compliant beams 718 and 720. The anchors 714connect to an aperture layer 725. The sidewall beams 716, 718 and 720are tall and narrow. The width of the sidewall beams 716, 718 and 720,as formed from the surface of the mold 703, is similar to the thicknessof the shutter material as deposited. In some implementations, the widthof sidewall beam 716 will be the same as the thickness of shutter 712.In some other implementations, the beam width will be about ½ thethickness of the shutter 712. The height of the sidewall beams 716, 718and 720 is determined by the thickness of the second sacrificialmaterial 705, or in other words, by the depth of the mold 703, ascreated during the patterning operation described in relation to FIG.7B. As long as the thickness of the deposited shutter material is chosento be less than about 2 microns, the process depicted in FIGS. 7A-7D iswell suited for the production of narrow beams. In fact, for manyapplications the thickness range of 0.1 to 2.0 micron is quite suitable.Conventional photolithography would limit the patterned features shownin FIGS. 7A, 7B and 7C to much larger dimensions, for instance allowingminimum resolved features no smaller than 2 microns or 5 microns.

FIG. 7D depicts an isometric view of the shutter assembly 700, formedafter the release operation in the above-described process, yieldingcompliant beams with cross sections of high aspect ratios. As long asthe thickness of the second sacrificial material 705 is, for example,greater than about 4 times larger than the thickness of the shuttermaterial, the resulting ratio of beam height to beam width will beproduced to a similar ratio, i.e., greater than about 4:1.

An optional stage, not illustrated above but included as part of theprocess leading to FIG. 7C, involves isotropic etching of the sidewallbeam material to separate or decouple the compliant load beams 720 fromthe compliant drive beams 718. For instance, the shutter material atpoint 724 has been removed from the sidewall through use of an isotropicetch. An isotropic etch is one whose etch rate is substantially the samein all directions, so that sidewall material in regions such as point724 is no longer protected. The isotropic etch can be accomplished inthe typical plasma etch equipment as long as a bias voltage is notapplied to the substrate 726. An isotropic etch also can be achievedusing wet chemical or vapor phase etching techniques. Prior to thisoptional fourth masking and etch stage, the sidewall beam materialexists essentially continuously around the perimeter of the recessedfeatures in the mold 703. The fourth mask and etch stage is used toseparate and divide the sidewall material, forming the distinct beams718 and 720. The separation of the beams 718 and 720 at point 724 isachieved through a fourth process of photoresist dispense, and exposurethrough a mask. The photoresist pattern in this case is designed toprotect the sidewall beam material against isotropic etching at allpoints except at the separation point 724.

As a final stage in the sidewall process, an encapsulating dielectric isdeposited around the outside surfaces of the sidewall beams 716, 718 and720.

In order to protect the shutter material deposited on the verticalsidewalls 709 of the mold 703 and to produce the sidewall beams 716, 718and 720 of substantially uniform cross section, some particular processguidelines can be followed. For instance, in FIG. 7B, the sidewalls 709can be made as vertical as possible. Slopes at the vertical sidewalls709 and/or exposed surfaces become susceptible to the anisotropic etch.In some implementations, the vertical sidewalls 709 can be produced bythe patterning operation at FIG. 7B, such as the patterning of thesecond sacrificial material 705 in an anisotropic fashion. The use of anadditional photoresist coating or a hard mask in conjunction withpatterning of the second sacrificial layer 705 allows the use ofaggressive plasmas and/or high substrate bias in the anisotropic etch ofthe second sacrificial material 705 while mitigating against excessivewear of the photoresist. The vertical sidewalls 709 also can be producedin photoimageable sacrificial materials as long as care is taken tocontrol the depth of focus during the UV exposure and excessiveshrinkage is avoided during final cure of the resist.

Another process guideline that helps during sidewall beam processingrelates to the conformality of the shutter material deposition. Thesurfaces of the mold 703 can be covered with similar thicknesses of theshutter material, regardless of the orientation of those surfaces,either vertical or horizontal. Such conformality can be achieved whendepositing with CVD. In particular, the following conformal techniquescan be employed: PECVD, low pressure chemical vapor deposition (LPCVD),and atomic or self-limited layer deposition (ALD). In the above CVDtechniques the growth rate of the thin film can be limited by reactionrates on a surface as opposed to exposing the surface to a directionalflux of source atoms. In some implementations, the thickness of materialgrown on vertical surfaces is at least 50% of the thickness of materialgrown on horizontal surfaces. Alternatively, shutter materials can beconformally deposited from solution by electroless plating orelectroplating, after a metal seed layer is provided that coats thesurfaces before plating.

FIG. 8A shows a cross-sectional view of an example display apparatus800. FIG. 8B shows a perspective view of a shutter assembly 801incorporated into the example display apparatus 800. Referring to FIGS.8A and 8B, the display apparatus 800 includes a shutter 802 supported byactuators 804 and anchors 806 between two light blocking layers 808 and810. The rear light blocking layer 808 is formed on a substrate 812, onwhich the shutter 802, actuators 804 and anchors 806 are likewiseformed. The front light blocking layer 810 is formed on a coversheet 814of the display. Each of the light blocking layers 808 and 810 includeapertures 816 defined through them, forming optical paths from abacklight 811 positioned behind the substrate 812, through a pair ofopposing apertures 816, and out of the front of the display apparatus800. The actuators 804 selectively move the shutter 802 into and out ofthese optical paths to obstruct the passage of light along the path,thereby forming an image.

The shutter 802 includes two light obstructing levels, a front lightobstructing level 820 and a rear light obstructing level 822. The frontand rear light obstructing levels 820 and 822 are connected by a sidewall 824. The front light obstructing level 820 is spaced a relativelyshort distance, between about 2 microns and about 10 microns, away fromthe front light blocking layer 810 and is generally aligned with edgesof the actuator 804. The distance is maintained by a set of spacers (notshown) separating the substrate 812 from the cover sheet 814. The rearlight obstructing level 822 is likewise spaced a relatively shortdistance, between about 2 and about 10 microns away, from the rear lightblocking layer 808. This distance is maintained by the anchors 806. Insome implementations, the front light obstructing level 820 ispositioned about the same distance from the front light blocking layer810 as the rear light obstructing level 822 is spaced from the rearlight blocking layer 808. In some other implementations, the separationdistances are different, but within about 3 microns of one another. As aresult of these similar separation distances, a light obstructingportion of the shutter 802 is proximate to, and can substantiallyobstruct the passage of light through the apertures 816 formed in, boththe rear and front light blocking layers 808 and 810.

The front and rear light obstructing levels 820 and 822 define a pair ofshutter apertures 823. The shutter apertures 823 are aligned with oneanother such that when the shutter 802 is in the open position, theoptical path through a corresponding pair of apertures 816 in the rearand front light blocking layers 808 and 810 is clear. Light is then ableto pass through an aperture 816 in the rear light blocking layer 808,through the shutter apertures 823, and through the aperture 816 in thefront light blocking layer 810, and out of the display apparatus 800.

The benefits of the two light obstructing levels 820 and 822 can be seenin relation to two illustrative light rays 850 a and 852 a. In FIG. 8A,the shutter 802 is in a closed position, and therefore should blocksubstantially all light passing through the rear apertures 816. Thelight ray 850 a demonstrates how the rear light obstructing level 822can help prevent off-angle light from bypassing the shutter 802 andleaking out of the display. The dashed line 850 b illustrates the paththe light ray 850 a would have taken were the rear light obstructinglevel 822 not included. The light ray 852 a demonstrates how the frontlight obstructing level 820 of the shutter 802 can help prevent lightthat reflects off of the rear light obstructing level 822 and reboundsoff of the front surface of the rear light blocking layer 808 fromundesirably leaving the display apparatus 800. The line 852 b shows thepath of the light ray 852 a were the front light obstructing level 820omitted from the shutter 802.

Moreover, as a result of the fabrication process used to fabricate theshutter assembly 801, portions 825 of the rear light obstructing level822 of the shutter 802 are substantially thicker than a remainder of therear light obstructing level 822. As shown in FIG. 8A, in someimplementations, when the shutter 802 is in the closed position, thesethicker portions 825, are aligned directly between pairs of opposingapertures 816. The extra thickness increases the light blocking abilityof the shutter 802, further improving the contrast ratio of the displayapparatus 800.

In some other implementations, the shutter assembly 801 is fabricated ona substrate located at the front of the display where the coversheet 814is shown in FIG. 8A (i.e., in a MEMS-down configuration). The shutterassembly 801 in such implementations extends down towards an apertureplate, on which a rear light blocking layer is formed, and which islocated in the position where the substrate 812 is shown in FIG. 8A. Insome other implementations, either the front or rear light blockinglayer 810 or 808, depending on the orientation of the shutter assembly801, is replaced with an elevated aperture layer. The elevated aperturelayer would be fabricated on the same substrate as the shutter assembly801. Such an elevated aperture layer includes a light blocking layerthat defines apertures positioned in alignment with the apertures 816defined by the light blocking layer 808 or 810.

FIG. 9 shows a flow diagram of an example method 900 for fabricating theshutter assembly 801 shown in FIGS. 8A and 8B. In brief overview, themethod 900 includes depositing and patterning a first layer ofsacrificial material (stage 902), depositing a first layer of structuralmaterial over the patterned first layer of sacrificial material (stage904), and patterning the first layer of structural material to define aproximal light obstructing level of the shutter and a shutter aperture(stage 906). The method 900 further includes depositing and patterning asecond layer of sacrificial material over the patterned first layer ofstructural material (stage 908), depositing a second layer of structuralmaterial over the patterned second layer of sacrificial material (stage910), and patterning the second layer of structural material to define adistal light obstructing level of the shutter (stage 912). FIGS. 10A-10Hshow cross sectional views of the results of each of the processingstages included in the method shown in FIG. 9.

Referring to FIGS. 8A, 8B, 9 and 10A-10H, the method 900 begins withdepositing and patterning a first layer of sacrificial material 1002(stage 902). More particularly, the first layer of sacrificial material1002 is deposited on top of a light blocking layer 1004, such as therear light blocking layer 808 shown in FIG. 8A. Prior to the depositionof the first layer of sacrificial material 1002, the rear light blockinglayer 1004 was patterned to form apertures, such as the apertures 816,also shown in FIG. 8A. The sacrificial material can be any of thematerials described above in relation to FIG. 6B as being suitable foruse as sacrificial material. The first layer of sacrificial material1002 can be applied through a spin-on process to yield a substantiallyplanar upper surface. In some implementations, the first layer ofsacrificial material 1002 is deposited to be about 1 micron to about 10microns thick. In some implementations, the first layer of sacrificialmaterial 1002 is deposited to be about 3 microns to about 5 micronsthick. This process yields the structure shown in FIG. 10A.

The first layer of sacrificial material 1002 is then patterned to formrecesses 1006 that will serve as molds for the lower portions ofanchors, such as the anchors 806, shown in FIGS. 8A and 8B. The firstlayer of sacrificial material 1002 can be patterned in a number of ways,depending on the materials used. More particularly, the first layer ofsacrificial material 1002 can be patterned by any of the sacrificiallayer patterning processes described above in relation to FIG. 6B. Forexample, for photosensitive sacrificial materials, the first layer ofsacrificial material 1002 can be directly exposed through a photo maskand developed, removing undesired sacrificial material. For other typesof sacrificial materials, a separate resist is first deposited on thefirst layer of sacrificial material 1002. The resist is then patternedand used as an etch mask in an etching process that removes portions ofthe layer sacrificial material 1002 exposed through the patternedresist. The results of this process are shown in FIG. 10B.

While not shown, in some implementations, several additional layers,including metal layers and inter-metal dielectric layers are depositedon top of the light blocking layer 1004 and are patterned prior to thedeposition of the first layer of sacrificial material 1002. Theseadditional layers form or include the control matrix that will controlthe shutter assembly when completed. In some other implementations, theadditional metal and inter-metal dielectric layers are deposited on thetransparent substrate 812 and patterned prior to deposition of the lightblocking layer 1004.

A first layer of structural material 1008 is then deposited on top ofthe patterned layer of sacrificial material 1002 (stage 904). Thestructural material is deposited using a CVD, PECVD, PVD, or ALDprocess, substantially conformally coating the exposed surfaces of thefirst layer of sacrificial material 1002 and any other surfaces exposedthrough the recesses 1006. The structural material can include one ormore layers of metal and/or semiconductor material, as described abovein relation to FIG. 6C as being suitable shutter materials. Thestructural material can be deposited to have a total thickness of lessthan about 2.0 microns. The results of this deposition stage (stage 904)are shown in FIG. 10C.

The first layer of structural material 1008 is patterned to form aproximal light obstructing level 1010 of the shutter assembly 801 (stage906). As used herein, the term proximal is used with respect to thesubstrate on which the shutter assembly 801 is being fabricated. For thedisplay apparatus 800 shown in FIG. 8A, the proximal light obstructinglevel 1010 would correspond to the rear light obstructing level 822. Thefront light obstructing level 820, being further from the substrate 812would be considered a distal light obstructing level.

The first layer of structural material 1008 can be patterned using oneor more etch processes. For example, in some implementations, the firstlayer of structural material 1008 is first etched using an anisotropicetch to remove unwanted structural material from the horizontal surfacesof the structure shown in FIG. 10C. A second isotropic etch can then beused to remove any unwanted structural material on the verticalsurfaces. In some other implementations, a single isotropic etch can beused to simultaneously remove material on both the horizontal andvertical surfaces of the structure.

Together, in some implementations, the one or more etching processesremove all of the first layer of structural material 1008 other than thematerial that will form the proximal light obstructing level 1010, asshown in FIG. 10D. Such etching defines the perimeter of the proximallight obstructing level 1010, as well as a proximal shutter aperture1011. In some other implementations, structural material is also left onone or more surfaces of the recesses 1006.

A second layer of sacrificial material 1012 is then deposited andpatterned (stage 908). The second layer of sacrificial material 1012 isdeposited over the structure shown in FIG. 10D using, for example, aspin-on process yielding the structure shown in FIG. 10E. The secondlayer of sacrificial material 1012 can be or can include the samematerial used for the first layer of sacrificial material 1002, or itcan include any of the other materials identified above as beingsuitable for use as a sacrificial material. The second layer ofsacrificial material 1012 is deposited to a thickness of between about 1and about 10 microns. In some implementations, the second layer ofsacrificial material 1012 is deposited to a thickness of between about 3and about 5 microns.

The second layer of sacrificial material 1012 is patterned to form anumber of additional recesses. Specifically, the patterning results intwo new anchor recesses 1014 positioned over the recesses 1006 formed inthe first layer of sacrificial material 1002 to serve as molds for theanchors 806. Two actuator recesses 1016 are formed. The sidewalls of theactuator recesses 1016 define molds for the beams of the electrostaticactuators 804. The actuator recesses 1016 extend down to the uppersurface of the first layer of sacrificial material 1002. As result, theedges of the actuator beams that are formed using this mold that areproximal to the substrate 812 are about the same distance away from thesubstrate 812 as the proximal light obstructing level 1010. In addition,two shutter recesses 1018 are formed in the second layer of sacrificialmaterial 1012. The shutter recesses 1018 define molds for the sidewalls824 of the shutter 802 and extend down to the remaining structuralmaterial from the first layer of structural material 1008, which formsthe proximal light obstructing level 1010. The resulting structure isshown in FIG. 10F.

A second layer of structural material 1020 is then deposited (stage 910)over the structure shown in 10F. The structural material substantiallyconformally coats the exposed surfaces of the structure, as shown inFIG. 10G. The second layer of structural material 1020 can be any of thestructural materials referred to above, including the same material usedfor the first layer of structural material 1008. It, too, can bedeposited to a thickness of less than about 2 microns.

Next, the second layer of structural material 1020 is patterned todefine a distal light obstructing level 1022 (stage 912) as shown inFIG. 10H. The front light obstructing level 820 shown in FIGS. 8A and 8Bis an example of a distal light obstructing level 1022. Moreparticularly, the second layer of structural material 1020 is patternedto define the periphery of the distal light blocking layer 1022 as wellas to define a distal shutter aperture 1024 in the distal light blockinglayer 1022. The distal shutter aperture 1024 is defined in alignmentwith the proximal shutter aperture 1011.

This patterning stage (stage 912) also defines the anchors 806 and thebeams of the electrostatic actuators 804. The front light obstructinglevel 1022 is spaced about the same distance over the substrate 812 asthe distal edges of the beams of the electrostatic actuators 804. Insome implementations, the patterning process may remove a small portionof structural material from the distal-most edges of the actuator beams.Thus, the front light obstructing level 1022 of the shutter 802 may bespaced slightly further above the substrate 812 than the distal ends ofthe actuator beams, while still being spaced about the same distance. Aswith the prior structural material patterning stage (stage 906), thesecond layer of structural material 1020 can likewise be patterned usingone or more etching processes including an anisotropic and/or anisotropic etch. The result of the patterning stage (stage 912) is shownin FIG. 10H. This structure can then be released yielding the shutterassembly 801 shown in FIGS. 8A and 8B.

As described above, both the proximal shutter aperture 1011 and thedistal shutter aperture 1024 are etched through a surface which, whenetched, is at the uppermost level of the material stack being etched.That is, neither shutter aperture 1011 or 1024 is being etched throughmaterial at the bottom of a recess formed in the material stack. Thisallows for more precise control of the etching process. When etchingstructural material located on the bottom of a recess, the sidewalls ofthe recess can provide a shadowing effect that limits precise patterningnear the sidewalls. No such shadow can interfere with the etching ofmaterial on the top of a material stack. Effectively depositing andpatterning a resist layer at the bottom of a recess can also posechallenges that are avoided by etching material at the top of a materialstack.

FIGS. 11A-11C show cross-sectional views of another example displayapparatus 1100. More particularly, FIGS. 11A-11C show a shutter assembly1102 incorporated into the display apparatus 1100 in each of threedistinct states the shutter assembly can be switched between. Theshutter assembly 1102 can enter into a closed state, as shown in FIG.11A or a partially open state, as shown in FIG. 11B; an open state, asshown in FIG. 11C. FIG. 11D shows an example perspective view of theshutter assembly 1102 incorporated into the display apparatus 1100 shownin FIGS. 11A-11C.

Referring to FIGS. 11A-11D, the display apparatus includes the shutterassembly 1102 disposed between a front light blocking layer 1104 and arear light blocking layer 1106. Pairs of apertures 1108 are definedthrough the front and rear light blocking layers 1104 and 1106. Theshutter assembly 1102 includes a shutter 1110, which is moved byelectrostatic actuators 1112 a and 1112 b into and out of an opticalpath formed through the pair of apertures 1108 formed in the front andrear light blocking layers 1104 and 1106.

The shutter assembly 1102 can achieves three distinct light modulatingstates due to the asymmetric shape of the shutter 1110. In particular,the shutter 1110 includes two light obstructing portions, a short lightobstructing portion 1114 and a long light obstructing portion 1116. Thelength of the short light obstructing portion 1114, along the directionof travel of the shutter 1110, is substantially shorter than the lengthof the long light obstructing portion 1116. In some implementations, theshort light obstructing portion 1114 has about half the length of thelong light obstructing portion 1116. In other implementations, the shortlight obstructing portion 1114 can have about ¼, ¾, or other fraction ofthe length of the long light obstructing portion 1116.

In operation, the shutter assembly 1102 moves the shutter 1110 laterallywith respect to the apertures 1108 formed in the front and rear lightblocking layers 1104 and 1106 on either side of the shutter 1110. Thelong light obstructing portion 1116 is long enough such that when theshutter assembly 1102 is in the closed state (as shown in FIG. 11A), thelong light obstructing portion 1116 fully obstructs light 1118 passingthrough the apertures 1108. In this state, a first electrostaticactuator 1112 a moves the shutter 1110 all the way to one side of theshutter assembly 1102.

The short light obstructing portion 1114 is short enough, such that whenthe shutter assembly 1102 is in a partially open state (shown in FIG.11B), the short light obstructing portion 1114 only partially obstructsthe apertures 1108. For example, in some implementations, the shortlight obstructing portion 1114 may be long enough to obstruct aboutone-quarter, about one-half, about three-quarters, or any other fractionof the area of the apertures 1108. In this state, a second electrostaticactuator 1112 b moves the shutter 1110 all the way to the other end ofthe shutter assembly 1102.

The light obstructing portions 1114 and 1116 are separated by a shutteraperture 1119 formed through the shutter 1110. When the shutter assembly1102 is in the open state (shown in FIGS. 11C and 11D), the shutteraperture 1119 is in substantial alignment with the apertures 1108 formedin the front and light blocking layers 1104 and 1106. The electrostaticactuators 1112 a and 1112 b are both relaxed (or unactuated) in thisstate, leaving the shutter 1110 in about the middle of the shutterassembly 1102. In some implementations, the light obstructing portions1114 and 1116 may each slightly obstruct the apertures 1108 in thisstate, but not to a significant degree.

Each of the light obstructing portions 1114 and 1116 includes both afront light obstructing level 1120 and a rear light obstructing level1122. The front light obstructing level 1120 and the rear lightobstructing level 1122 are connected by sidewalls 1124 that surround theshutter aperture 1119. In some implementations, the front lightobstructing level 1120 is positioned about the same distance from thefront light blocking layer 1104 as the rear light obstructing level 1122is spaced from the rear light obstructing layer 1106. In some otherimplementations, the separation distances are different, but withinabout 3 microns of one another. As a result, a light obstructing levelof the shutter 1110 is proximate to, and can substantially obstruct thepassage of light through the apertures 1108 formed in both the front andrear light blocking layers 1104 and 1106.

While the shutter assembly 1102 is shown in a MEMS-up configuration, insome other implementations, the shutter assembly 1102 can be integratedinto a display apparatus in a MEMS-down configuration. In some otherimplementations, either the front or rear light blocking layer 1104 or1106, depending on the orientation of the shutter assembly 1102 (i.e.,MEMS-up or MEMS-down), is replaced with an elevated aperture layer. Theelevated aperture layer would be fabricated on the same substrate as theshutter assembly 801. Such an elevated aperture layer includes a lightblocking layer that defines apertures positioned in alignment with theapertures 1108 defined by the light blocking layers 1104 or 1106. Inaddition, in some implementations, the shutter assembly 1102 can includeshutter that includes only one light obstructing level. An example ofsuch a shutter assembly is shown in FIG. 11E.

FIG. 11E shows an example perspective view of another example shutterassembly 1150 similar to the shutter assembly 1102 shown in FIGS.11A-11D. More particularly, the shutter assembly 1150 includes a shutter1160 that has only a single light obstructing level, instead of havingthe separate front and rear light blocking levels 1120 and 1122 includedin the shutter 1110 shown in FIGS. 11A-11D. Similar to the shutter 1110,though, the shutter 1160 includes both short and long light blockingportions 1114 and 1116. The shutter 1160 is also supported by opposingactuators 1112 a and 1112 b, and is supported over a light blockinglayer 1106 by anchors 1128. The shutter assembly 1150 can be operated inthe same fashion as the shutter assembly 1102, moving the shutter 1160between three states, as shown in FIGS. 11A-11C.

FIGS. 12A-12H show cross sectional views of example stages of thefabrication of the shutter assembly 1102 shown in FIGS. 11A-11D. Likethe shutter assembly 801, shown in FIG. 8, the shutter assembly 1102 canbe fabricated using the same general fabrication process 900 shown inFIG. 9. As shown in FIGS. 12A and 12B, the fabrication of the shutterassembly 1102 begins with the deposition and patterning of a first layerof sacrificial material 1202 (stage 902). Specifically, the first layerof sacrificial material 1202 is deposited on a substrate 1204 over apatterned light blocking layer 1206. The light blocking layer 1206 hasbeen patterned to form apertures 1108 that form part of the optical pathdescribed above. The first layer of sacrificial material 1202 can be orinclude any of the sacrificial materials described above. The firstlayer of sacrificial material 1202 is patterned to form recesses 1208that will serve as molds for the bases of the anchors 1128 shown inFIGS. 11A-D.

A first layer of structural material 1210 is then deposited over thepatterned first layer of sacrificial material 1202 (stage 904). Thefirst layer of structural material 1210 can be or include any of thestructural materials described above, including, in someimplementations, a multi-layer stack of such materials. It can bedeposited to a thickness of less than about 2.0 microns. The result ofsuch deposition is shown in FIG. 12C.

The first layer of structural material 1210 is patterned to define aproximal light obstructing level of the shutter 1110, i.e., the rearlight obstructing level 1122 and the shutter aperture 1119 (stage 906).In this patterning process, the first layer of structural material 1210is removed except where it will form the rear light obstructing level1122. The shutter aperture 1119 is patterned to be off-center withrespect to the length of the rear light obstructing level 1122, therebydefining the sizes of the short and long light blocking portions 1114and 1116. The patterning, in some implementations, is carried out usingtwo etches, an anisotropic etch to remove unwanted structural materialon horizontal surfaces of the structure and an isotropic etch to removeundesired structural material on vertical surfaces of the structure,such as the sidewalls of the recesses 1208. The results of thepatterning process are shown in FIG. 12D.

After the proximal light obstructing level and the shutter aperture aredefined (stage 906), a second layer of sacrificial material 1212 isdeposited over the patterned first layer of structural material 1210 (asshown in FIG. 12E), and is patterned (stage 908), yielding the structureshown in FIG. 12F. Specifically, the second layer of sacrificialmaterial 1212 is patterned to form anchor recesses 1214, actuator recess1216, and a shutter aperture recess 1218.

A second layer of structural material 1220 is then deposited (stage 910)over the patterned second layer of sacrificial material 1212. The secondlayer of structural material 1220 coats the upper surface of the secondlayer of sacrificial material 1212, as well as the sidewalls and bottomsof the recesses 1214, 12126, and 1218. The second layer of structuralmaterial 1220 can be or include the same materials and be substantiallythe same thickness as the first layer of structural material 1210. Theresult of this deposition is shown in FIG. 12G.

The second layer of structural material 1220 is then patterned to definethe distal light obstructing level of the shutter 1110 (stage 912);i.e., the front light obstructing level 1120. At the same time, thesecond layer of structural material 1220 is patterned to define theanchors 1128, the actuators 1112 a and 1112 b, and to reopen the shutteraperture 1119, which was covered by the second layer of structuralmaterial. As with the previous structural material patterning stage, thesecond layer of structural material 1220 can be patterned using a singleisotropic etch or a two-phase etch process, including an anisotropicetch and a isotropic etch. The resulting structure is shown in FIG. 12H.After the patterning stage (stage 912), the structure is released,yielding the shutter assembly 1102 shown in FIGS. 11A-D.

FIG. 13 shows a flow diagram of another representation of a method 1300of manufacturing the shutter assembly 1102 shown in FIGS. 11A-11D. Themethod includes defining a first aperture in a first light blockinglayer (stage 1302), depositing a first layer of sacrificial materialover the first light blocking layer (stage 1304), and depositing atleast a first layer of structural material over the first layer ofsacrificial material (stage 1306). The method 1300 further includespatterning at least the first layer of structural material to define aperimeter of a shutter and a shutter aperture through the shutter,wherein the shutter perimeter and the shutter aperture are configuredsuch that the shutter includes asymmetric first and second lightobstructing portions positioned on opposite sides of the shutteraperture along an axis of motion 1130 (shown in FIGS. 11A-11C) of theshutter (stage 1308) and patterning at least the first layer ofstructural material to define at least one actuator configured to movethe shutter along the axis of motion into a relaxed state in whichneither the first nor the second light obstructing portionssubstantially obstructs light passing through the first aperture, afirst actuated state in which the first light obstructing portionobstructs a fraction of light passing through the first aperture, and asecond actuated state in which the second light obstructing portionobstructs substantially all of the light passing through the firstaperture (stage 1310).

As set forth above, the method 1300 includes defining a first aperture,such as the aperture 1108, shown in FIGS. 11A-11C and FIGS. 12A-12H, ina first light blocking layer (stage 1302), such as the light blockinglayer 1206 shown in FIG. 12. For example, the apertures can be definedusing one of a number of common photolithography processes to etchopenings through a light blocking layer. In some implementations, thefirst light blocking layer is light absorbing. In some otherimplementations, the first light absorbing layer is reflective. In someother implementations, the first light blocking layer is reflective inone direction and absorptive in the opposite direction.

A first layer of sacrificial material is then deposited over the firstlight blocking layer (stage 1304). This process is similar to that shownin FIG. 12A. At least a first layer of structural material is thendeposited over the first layer of sacrificial material (stage 1306). Insome implementations, more than one layer of structural material isdeposited. In some such implementations, the first layer of structuralmaterial is patterned, as discussed further below, before a second layerof sacrificial material is deposited over the first layer of structuralmaterial, and before a second layer of structural material is deposited.The structural material layer deposition process is described furtherabove in relation to FIGS. 12C and 12G.

The method 1300 further includes patterning the deposited layer(s) ofstructural material (stages 1308 and 1310). More particularly, thelayer(s) of structural material are patterned to define a shutter, suchas the shutter 1110 shown in FIGS. 11A-11E (stage 1308) and at least oneactuator, such as actuators 1112 a and 1112 b, also shown in FIGS.11A-11E (stage 1310). The shutter is defined by patterning the perimeterof the shutter as well as a shutter aperture, such as the shutteraperture 1109 shown in FIGS. 11A-11E. The perimeter and shutter apertureare patterned such that the shutter includes asymmetric first and secondlight blocking portions on either side of the shutter aperture along anaxis of motion of the shutter. The short and long light blockingportions 1114 and 1116 of the shutter 1110 shown in FIG. 11 are examplesof such asymmetric first and second light blocking portions.

The at least one actuator is defined such that the actuator(s) can movethe shutter along the axis of motion between three states. In a relaxedstate, neither the first nor the second light blocking portionsubstantially obstructs light passing through the aperture defined inthe first light blocking layer in stage 1302. In a first actuated state,the at least one actuator moves the shutter into a position in whichfirst light obstructing portion obstructs a fraction, but notsubstantially all, of the light passing through the first aperture. In asecond actuated state, the at least one actuator moves the shutter intoa position in which the second light obstructing portion obstructssubstantially all of the light passing through the first aperture. Thepatterning process resulting in the above-described shutter and at leastone actuator is described above in relation to FIGS. 12D and 12H. Theoperation of the at least one actuator is shown in FIGS. 11A-11C.

FIGS. 14 and 15 show system block diagrams of an example display device40 that includes a set of display elements. The display device 40 canbe, for example, a smart phone, a cellular or mobile telephone. However,the same components of the display device 40 or slight variationsthereof are also illustrative of various types of display devices suchas televisions, computers, tablets, e-readers, hand-held devices andportable media devices.

The display device 40 includes a housing 41, a display 30, an antenna43, a speaker 45, an input device 48 and a microphone 46. The housing 41can be formed from any of a variety of manufacturing processes,including injection molding, and vacuum forming. In addition, thehousing 41 may be made from any of a variety of materials, including,but not limited to: plastic, metal, glass, rubber and ceramic, or acombination thereof. The housing 41 can include removable portions (notshown) that may be interchanged with other removable portions ofdifferent color, or containing different logos, pictures, or symbols.

The display 30 may be any of a variety of displays, including abi-stable or analog display, as described herein. The display 30 alsocan be configured to include a flat-panel display, such as plasma,electroluminescent (EL) displays, OLED, super twisted nematic (STN)displays, LCD, or thin film transistors (TFT) LCD, or a non-flat-paneldisplay, such as a cathode ray tube (CRT) or other tube device. Inaddition, the display 30 can include a mechanical light modulator-baseddisplay as described herein.

The components of the display device 40 are schematically illustrated inFIG. 14. The display device 40 includes a housing 41 and can includeadditional components at least partially enclosed therein. For example,the display device 40 includes a network interface 27 that includes anantenna 43 which can be coupled to a transceiver 47. The networkinterface 27 may be a source for image data that could be displayed onthe display device 40. Accordingly, the network interface 27 is oneexample of an image source module, but the processor 21 and the inputdevice 48 also may serve as an image source module. The transceiver 47is connected to a processor 21, which is connected to conditioninghardware 52. The conditioning hardware 52 may be configured to conditiona signal (such as filter or otherwise manipulate a signal). Theconditioning hardware 52 can be connected to a speaker 45 and amicrophone 46. The processor 21 also can be connected to an input device48 and a driver controller 29. The driver controller 29 can be coupledto a frame buffer 28, and to an array driver 22, which in turn can becoupled to a display array 30. One or more elements in the displaydevice 40, including elements not specifically depicted in FIG. 14, canbe configured to function as a memory device and be configured tocommunicate with the processor 21. In some implementations, a powersupply 50 can provide power to substantially all components in theparticular display device 40 design.

The network interface 27 includes the antenna 43 and the transceiver 47so that the display device 40 can communicate with one or more devicesover a network. The network interface 27 also may have some processingcapabilities to relieve, for example, data processing requirements ofthe processor 21. The antenna 43 can transmit and receive signals. Insome implementations, the antenna 43 transmits and receives RF signalsaccording to the IEEE 16.11 standard, including IEEE 16.11(a), (b), or(g), or the IEEE 802.11 standard, including IEEE 802.11a, b, g, n, andfurther implementations thereof. In some other implementations, theantenna 43 transmits and receives RF signals according to the Bluetooth®standard. In the case of a cellular telephone, the antenna 43 can bedesigned to receive code division multiple access (CDMA), frequencydivision multiple access (FDMA), time division multiple access (TDMA),Global System for Mobile communications (GSM), GSM/General Packet RadioService (GPRS), Enhanced Data GSM Environment (EDGE), TerrestrialTrunked Radio (TETRA), Wideband-CDMA (W-CDMA), Evolution Data Optimized(EV-DO), 1xEV-DO, EV-DO Rev A, EV-DO Rev B, High Speed Packet Access(HSPA), High Speed Downlink Packet Access (HSDPA), High Speed UplinkPacket Access (HSUPA), Evolved High Speed Packet Access (HSPA+), LongTerm Evolution (LTE), AMPS, or other known signals that are used tocommunicate within a wireless network, such as a system utilizing 3G, 4Gor 5G technology. The transceiver 47 can pre-process the signalsreceived from the antenna 43 so that they may be received by and furthermanipulated by the processor 21. The transceiver 47 also can processsignals received from the processor 21 so that they may be transmittedfrom the display device 40 via the antenna 43.

In some implementations, the transceiver 47 can be replaced by areceiver. In addition, in some implementations, the network interface 27can be replaced by an image source, which can store or generate imagedata to be sent to the processor 21. The processor 21 can control theoverall operation of the display device 40. The processor 21 receivesdata, such as compressed image data from the network interface 27 or animage source, and processes the data into raw image data or into aformat that can be readily processed into raw image data. The processor21 can send the processed data to the driver controller 29 or to theframe buffer 28 for storage. Raw data typically refers to theinformation that identifies the image characteristics at each locationwithin an image. For example, such image characteristics can includecolor, saturation and gray-scale level.

The processor 21 can include a microcontroller, CPU, or logic unit tocontrol operation of the display device 40. The conditioning hardware 52may include amplifiers and filters for transmitting signals to thespeaker 45, and for receiving signals from the microphone 46. Theconditioning hardware 52 may be discrete components within the displaydevice 40, or may be incorporated within the processor 21 or othercomponents.

The driver controller 29 can take the raw image data generated by theprocessor 21 either directly from the processor 21 or from the framebuffer 28 and can re-format the raw image data appropriately for highspeed transmission to the array driver 22. In some implementations, thedriver controller 29 can re-format the raw image data into a data flowhaving a raster-like format, such that it has a time order suitable forscanning across the display array 30. Then the driver controller 29sends the formatted information to the array driver 22. Although adriver controller 29, such as an LCD controller, is often associatedwith the system processor 21 as a stand-alone Integrated Circuit (IC),such controllers may be implemented in many ways. For example,controllers may be embedded in the processor 21 as hardware, embedded inthe processor 21 as software, or fully integrated in hardware with thearray driver 22.

The array driver 22 can receive the formatted information from thedriver controller 29 and can re-format the video data into a parallelset of waveforms that are applied many times per second to the hundreds,and sometimes thousands (or more), of leads coming from the display'sx-y matrix of display elements.

In some implementations, the driver controller 29, the array driver 22,and the display array 30 are appropriate for any of the types ofdisplays described herein. For example, the driver controller 29 can bea conventional display controller or a bi-stable display controller.Additionally, the array driver 22 can be a conventional driver or abi-stable display driver. Moreover, the display array 30 can be aconventional display array or a bi-stable display array. In someimplementations, the driver controller 29 can be integrated with thearray driver 22. Such an implementation can be useful in highlyintegrated systems, for example, mobile phones, portable-electronicdevices, watches or small-area displays.

In some implementations, the input device 48 can be configured to allow,for example, a user to control the operation of the display device 40.The input device 48 can include a keypad, such as a QWERTY keyboard or atelephone keypad, a button, a switch, a rocker, a touch-sensitivescreen, a touch-sensitive screen integrated with the display array 30,or a pressure- or heat-sensitive membrane. The microphone 46 can beconfigured as an input device for the display device 40. In someimplementations, voice commands through the microphone 46 can be usedfor controlling operations of the display device 40.

The power supply 50 can include a variety of energy storage devices. Forexample, the power supply 50 can be a rechargeable battery, such as anickel-cadmium battery or a lithium-ion battery. In implementationsusing a rechargeable battery, the rechargeable battery may be chargeableusing power coming from, for example, a wall socket or a photovoltaicdevice or array. Alternatively, the rechargeable battery can bewirelessly chargeable. The power supply 50 also can be a renewableenergy source, a capacitor, or a solar cell, including a plastic solarcell or solar-cell paint. The power supply 50 also can be configured toreceive power from a wall outlet.

In some implementations, control programmability resides in the drivercontroller 29 which can be located in several places in the electronicdisplay system. In some other implementations, control programmabilityresides in the array driver 22. The above-described optimization may beimplemented in any number of hardware and/or software components and invarious configurations.

As used herein, a phrase referring to “at least one of” a list of itemsrefers to any combination of those items, including single members. Asan example, “at least one of: a, b, or c” is intended to cover: a, b, c,a-b, a-c, b-c, and a-b-c.

The various illustrative logics, logical blocks, modules, circuits andalgorithm processes described in connection with the implementationsdisclosed herein may be implemented as electronic hardware, computersoftware, or combinations of both. The interchangeability of hardwareand software has been described generally, in terms of functionality,and illustrated in the various illustrative components, blocks, modules,circuits and processes described above. Whether such functionality isimplemented in hardware or software depends upon the particularapplication and design constraints imposed on the overall system.

The hardware and data processing apparatus used to implement the variousillustrative logics, logical blocks, modules and circuits described inconnection with the aspects disclosed herein may be implemented orperformed with a general purpose single- or multi-chip processor, adigital signal processor (DSP), an application specific integratedcircuit (ASIC), a field programmable gate array (FPGA) or otherprogrammable logic device, discrete gate or transistor logic, discretehardware components, or any combination thereof designed to perform thefunctions described herein. A general purpose processor may be amicroprocessor, or, any conventional processor, controller,microcontroller, or state machine. A processor also may be implementedas a combination of computing devices, e.g., a combination of a DSP anda microprocessor, a plurality of microprocessors, one or moremicroprocessors in conjunction with a DSP core, or any other suchconfiguration. In some implementations, particular processes and methodsmay be performed by circuitry that is specific to a given function.

In one or more aspects, the functions described may be implemented inhardware, digital electronic circuitry, computer software, firmware,including the structures disclosed in this specification and theirstructural equivalents thereof, or in any combination thereof.Implementations of the subject matter described in this specificationalso can be implemented as one or more computer programs, i.e., one ormore modules of computer program instructions, encoded on a computerstorage media for execution by, or to control the operation of, dataprocessing apparatus.

If implemented in software, the functions may be stored on ortransmitted over as one or more instructions or code on acomputer-readable medium. The processes of a method or algorithmdisclosed herein may be implemented in a processor-executable softwaremodule which may reside on a computer-readable medium. Computer-readablemedia includes both computer storage media and communication mediaincluding any medium that can be enabled to transfer a computer programfrom one place to another. A storage media may be any available mediathat may be accessed by a computer. By way of example, and notlimitation, such computer-readable media may include RAM, ROM, EEPROM,CD-ROM or other optical disk storage, magnetic disk storage or othermagnetic storage devices, or any other medium that may be used to storedesired program code in the form of instructions or data structures andthat may be accessed by a computer. Also, any connection can be properlytermed a computer-readable medium. Disk and disc, as used herein,includes compact disc (CD), laser disc, optical disc, digital versatiledisc (DVD), floppy disk, and blue-ray disc where disks usually reproducedata magnetically, while discs reproduce data optically with lasers.Combinations of the above should also be included within the scope ofcomputer-readable media. Additionally, the operations of a method oralgorithm may reside as one or any combination or set of codes andinstructions on a machine readable medium and computer-readable medium,which may be incorporated into a computer program product.

Various modifications to the implementations described in thisdisclosure may be readily apparent to those skilled in the art, and thegeneric principles defined herein may be applied to otherimplementations without departing from the spirit or scope of thisdisclosure. Thus, the claims are not intended to be limited to theimplementations shown herein, but are to be accorded the widest scopeconsistent with this disclosure, the principles and the novel featuresdisclosed herein.

Additionally, a person having ordinary skill in the art will readilyappreciate, the terms “upper” and “lower” are sometimes used for ease ofdescribing the figures, and indicate relative positions corresponding tothe orientation of the figure on a properly oriented page, and may notreflect the proper orientation of any device as implemented.

Certain features that are described in this specification in the contextof separate implementations also can be implemented in combination in asingle implementation. Conversely, various features that are describedin the context of a single implementation also can be implemented inmultiple implementations separately or in any suitable subcombination.Moreover, although features may be described above as acting in certaincombinations and even initially claimed as such, one or more featuresfrom a claimed combination can in some cases be excised from thecombination, and the claimed combination may be directed to asubcombination or variation of a subcombination.

Similarly, while operations are depicted in the drawings in a particularorder, this should not be understood as requiring that such operationsbe performed in the particular order shown or in sequential order, orthat all illustrated operations be performed, to achieve desirableresults. Further, the drawings may schematically depict one more exampleprocesses in the form of a flow diagram. However, other operations thatare not depicted can be incorporated in the example processes that areschematically illustrated. For example, one or more additionaloperations can be performed before, after, simultaneously, or betweenany of the illustrated operations. In certain circumstances,multitasking and parallel processing may be advantageous. Moreover, theseparation of various system components in the implementations describedabove should not be understood as requiring such separation in allimplementations, and it should be understood that the described programcomponents and systems can generally be integrated together in a singlesoftware product or packaged into multiple software products.Additionally, other implementations are within the scope of thefollowing claims. In some cases, the actions recited in the claims canbe performed in a different order and still achieve desirable results.

What is claimed is:
 1. An apparatus, comprising: a first light blockinglayer including a first aperture formed therein; and a shutter suspendedover the first light blocking layer, wherein the shutter includes: afirst sidewall and a second sidewall both oriented substantially normalto the first light blocking layer; a proximal light obstructing levelcoupled to and extending outward from a first end of both the first andsecond sidewalls located proximate to the first light blocking layer;and a distal light obstructing level coupled to and extending outwardfrom a second end of both the first and second sidewalls located distalto the first light blocking layer relative to the proximal lightobstructing level, wherein a portion of the proximal light obstructinglevel positioned between the first and second sidewalls is substantiallythicker than another portion of the proximal light obstructing levelpositioned outside of the first and second sidewalls, and the thickerportion of the proximal light obstructing level is at a position in theshutter such that when the shutter is in a closed position, the thickerportion is in alignment with the first aperture defined by the firstlight blocking layer.
 2. The apparatus of claim 1, wherein the shutterincludes: a distal shutter aperture defined through the distal lightobstructing level; and a proximal shutter aperture defined through theproximal light obstructing level, wherein the proximal shutter apertureis aligned with the distal shutter aperture.
 3. The apparatus of claim1, wherein the shutter is configured such that in a closed position, aportion of the proximal light obstructing level overlaps an edge of thefirst aperture defined in the first light blocking layer and a portionof the distal light obstructing level overlaps an edge of a secondaperture defined in a second light blocking layer.
 4. The apparatus ofclaim 3, wherein the second light blocking layer is positioned on anopposite side of the shutter from the first light blocking layer.
 5. Theapparatus of claim 4, wherein the proximal light obstructing level isspaced from the first light blocking layer by about the same distance asthe distal light obstructing level is spaced from the second lightblocking layer.
 6. The apparatus of claim 4, wherein the proximal lightobstructing level is spaced from the first light blocking layer by adistance that is less than about 3 microns different from the distancewith which the distal light obstructing level is spaced from a secondlight blocking layer positioned opposite the shutter from the firstlight blocking layer.
 7. The apparatus of claim 1, further comprising anelectrostatic actuator for moving the shutter into and out of an opticalpath through the aperture.
 8. The apparatus of claim 7, wherein theelectrostatic actuator includes at least one beam electrode positionedadjacent the shutter, and the proximal light obstructing level ispositioned at about the same height over a substrate as a proximal edgeof the beam electrode.
 9. The apparatus of claim 8, wherein the distallight obstructing level is positioned at about the same height over asubstrate as a distal edge of the beam electrode.
 10. The apparatus ofclaim 1, comprising: a display including the shutter; a processor thatis configured to communicate with the display, the processor beingconfigured to process image data; and a memory device that is configuredto communicate with the processor.
 11. The apparatus of claim 10,further comprising: a driver circuit configured to send at least onesignal to the display; and wherein the processor is further configuredto send at least a portion of the image data to the driver circuit. 12.The apparatus of claim 10, further comprising: an image source moduleconfigured to send the image data to the processor, wherein the imagesource module comprises at least one of a receiver, transceiver, andtransmitter.
 13. The apparatus of claim 10, further comprising: an inputdevice configured to receive input data and to communicate the inputdata to the processor.
 14. A method for fabricating a display element,comprising: depositing and patterning a first layer of sacrificialmaterial over a substrate; depositing a first layer of structuralmaterial over the patterned first layer of sacrificial material;patterning the first layer of structural material to define a proximallight obstructing level of a shutter; depositing and patterning a secondlayer of sacrificial material over the patterned first layer ofstructural material; depositing a second layer of structural materialover the patterned second layer of sacrificial material; and patterningthe second layer of structural material to define a distal lightobstructing level of the shutter, a first sidewall, and a secondsidewall, both the first and second sidewalls oriented substantiallynormal to substrate, wherein a portion of the proximal light obstructinglevel positioned between the first and second sidewalls is substantiallythicker than another portion of the proximal light obstructing levelpositioned outside of the first and second sidewalls, and the thickerportion of the proximal light obstructing level is at a position in theshutter such that when the shutter is in a closed position, the thickerportion is in alignment with a first aperture defined by a first lightblocking layer.
 15. The method of claim 14, wherein patterning thesecond layer of sacrificial material includes forming a recess in thesecond layer of sacrificial material extending down to a portion of thefirst layer of structural material forming the proximal lightobstructing level of the shutter.
 16. The method of claim 14, whereindepositing the second layer of structural material includes depositing aportion of the second layer of structural material directly over aportion of the first layer of structural material.
 17. The method ofclaim 14, further comprising removing the first and second layers ofsacrificial material to release the proximal and distal lightobstructing levels.
 18. The method of claim 14, further comprisingpatterning the first layer of structural material to define a firstshutter aperture.
 19. The method of claim 18, further comprisingdefining a second shutter aperture in the second layer of structuralmaterial, such that the second shutter aperture aligns with the firstshutter aperture defined in the first layer of structural material. 20.The method of claim 19, wherein the second shutter aperture is definedin a portion of the second layer of structural material positioned atthe top of a material stack including the substrate, the first layer ofsacrificial material, and the second layer of sacrificial material. 21.The method of claim 19, wherein the second shutter aperture is definedin a portion of the second layer of structural material positioned atthe bottom of a recess patterned into the second layer of sacrificialmaterial.